Software Requirements under the section "Introduction to Genetics".
Course "Genetics with the basics of selection" for biology students
Genetics is the science of the laws of heredity, inheritance and variability, its place in the system natural sciences. Subject of genetics. The concept of heredity and variability. Basic approaches to the study of heredity and variability of organisms (molecular, chromosomal, cellular, organismal, population).
Objects of genetics. Genetic analysis and its components (hybridological, cytological, mathematical, mutational, molecular genetic, ontogenetic, population, etc.). basic principles of hybridological analysis. The connection of genetics with other sciences and branches of biology, Agriculture and medicine.
Main stages of development classical genetics(the theory of pangenesis by Charles Darwin, the discovery of the laws of heredity by G. Mendel, the nuclear hypothesis of heredity by T. Morgan, the discovery of the law homologous series N.I. Vavilov, development of population genetics methods by S.S. Chetverikov, theory of induced mutagenesis by G.A. Nadsona, G.S. Filippov and G. Meller, proof of the complex structure of the gene by A.S. Serebrovsky); main stages in the development of molecular genetics (creation of the concept of “one gene – one enzyme”), establishment genetic role nucleic acids, the discovery of genetic information exchange in bacteria. Main sections modern genetics: molecular genetics, cytogenetics, immunogenetics, biochemical and physiological genetics. Radiation genetics, population genetics, ontogenetics, mathematical genetics, environmental genetics. Genetics of microorganisms, plants, animals and humans.
The practical significance of genetics for agriculture, the biochemical industry, for medicine and pedagogy. The importance of genetics in the development of dialectical-materialist philosophy. The ideological significance of genetics and its place in the course general biology in middle school.
Course "Veterinary Genetics" for veterinary students
Genetics is one of the most important sciences modern biology. Subject of genetics. The essence of the phenomena of heredity and variability. Veterinary genetics is a science that studies the role of heredity in the etiology and pathogenesis of diseases and methods of their prevention, monitoring of hidden genetic defects, identification of heterozygous carriers, elimination of harmful genes in populations, analysis of breeding animals to identify carriers of chromosome aberrations and their culling, study of the genetics of immunity, pathogenicity and virulence of microorganisms and their interaction with macroorganisms, development of methods early detection resistance to diseases. Control of environmental mutagens, analysis of hereditary cell structures, characteristics and functions of organisms, explanation of genetically determined reactions of the body to drugs, creation of disease-resistant breeds, types and lines of animals based on the use of methods of veterinary selection and biotechnology. Connection of genetics with other sciences. Methods of genetics: hybridological, genealogical, biochemical, cytogenetic, phenogenetic, immunogenetic, ontogenetic, population statistical, molecular genetic, etc. Study of the phenomena of heredity at the molecular, subcellular, organismal and population levels. The main stages of development of genetics. The contribution of domestic scientists to the development of genetics (N.I. Vavilov, A.S. Serebrovsky, G.A. Nadson, G.S. Filippov, Yu.A. Filipchenko, G.D. Karpechenko, S.S. Chetverikov, B L. Astaurov, N. P. Dubinin, D. K. Belyaev, O. A. Ivanova, etc.). The importance of genetics for the formation of a scientific worldview. Genetics and the welfare of humanity. The role of genetics in veterinary medicine, animal husbandry, medicine. Historical aspects veterinary genetics. Prospects for the development of genetics.
Course "Genetics and Biometrics" for animal engineering students
Subject of genetics. Genetics is one of the fundamental sciences of modern biology. The main stages of development of genetics. The role of domestic scientists in the development of genetics. Genetics as a theoretical basis for agricultural selection. animals. The essence of the phenomena of heredity and variability at the molecular, subcellular, cellular, organismal, population levels. The main types of heredity: nuclear and cytoplasmic heredity. True, false and transitional heredity. Types of variability: ontogenetic, modification, combinative and mutational. The significance of modification variability for livestock farming practices. The use of other types of variability in breeding work. Correlative variability. Creative role human in the formation of heredity and variability of organisms. Genetics methods: hybridological, genealogical, phenogenetic, population, mutation, recombination, biometric analysis, methods of biochemical genetics, methods of immunogenetics. Current state and problems of genetics in connection with current problems humanity (food resources, population growth, human health, protection environment etc.). Achievements of modern genetics and ways of its further development.
Genetics is the science of heredity and variability of organisms and methods of controlling them. More full definition is as follows: genetics is a science that studies the phenomena of variability and heredity, the patterns of storage, transmission and implementation processes genetic information at the molecular, cellular, organismal and population levels. The term " genetics"(from Latin word geneo - generate) as the name for this science was proposed in 1905 by the English scientist William Bateson.
1.1. Subject, purpose, problems and tasks of genetics
Every science has its own item research, target, more private tasks research and methods research. The tasks of science in different periods its development may vary depending on the problems that arise on the way to achieving the goal facing this science.
1.1.1. Subject and purpose of genetics
Genetics studies two basic properties of organisms - heredity And variability. These two fundamental properties of living things are the subject of genetic research.
Genetics sets itself two goals: Firstly, cognition of patterns heredity and variability and, secondly, finding ways practical use these patterns. The ways to achieve both goals are constantly and closely intertwined. This is due to the fact that the solution of practical problems is based on conclusions obtained from the study of theoretical problems. At the same time, when solving practical problems, factual data is often obtained that is important for expanding and deepening theoretical concepts.
1.1.1.1. Heredity
Heredity - this is the property of organisms to transmit their characteristics and developmental characteristics to their offspring during reproduction.
Each type of plant or animal from generation to generation retains its characteristic features: a birch tree reproduces a birch tree, a duck hatches ducklings, a cat gives birth to kittens. Moreover, each type of plant and animal, no matter where it is transported and in what conditions it is placed, if it retains the ability to reproduce under these conditions, will reproduce its characteristics in its offspring.
Heredity ensures material and functional continuity between generations of organisms. Heredity manifests itself in the continuity of living matter during the change of generations. Some species can remain relatively unchanged for hundreds of millions of years. For example, the modern opossum differs little from the opossum of the early Cretaceous period. Heredity maintains a certain order in the variability of living beings.
Heredity is inextricably linked with the process of reproduction, and reproduction is with cell division and reproduction of its structure and functions.
The emergence of a new daughter generation during sexual reproduction occurs when the female and male germ cells merge. The egg and sperm are the bridge that ensures material continuity between generations. But, besides sexual, there is asexual reproduction, in which a whole organism is reproduced from a group of somatic cells or from a single cell. If a living hydra is cut into pieces, then a whole hydra of the same species grows from the individual pieces. In the same way, from individual pieces of a begonia leaf, a whole plant similar to the original one is restored.
The transfer of certain properties is only one aspect of heredity. Its second side is to ensure accurate transmission of the type of development specific to each organism, the formation during ontogenesis certain signs and properties, as well as a certain type of metabolism.
The material basis of heredity is all the elements of a cell that have the property of reproducing themselves and being distributed among daughter cells during the process of division. It turned out that especially important role play the processes of reproduction and distribution of specific structures of the cell nucleus - chromosomes. Heredity due to structures cell nucleus, called nuclear (chromosomal) inheritance . At the same time, a number of genetic structures may be located outside the nucleus (in other cell organelles and in the cytoplasm itself). Heredity due to cellular structures, located outside the core are called cytoplasmic (extranuclear, extrachromosomal) .
It is necessary to clearly distinguish between two concepts used in genetics - heredity and inheritance. The concept " heredity"reflects the property of genes to determine: a) the construction of specific protein molecules, b) the development of a trait and c) the structural plan of the organism. The concept " inheritance“characterizes the process of transferring hereditary properties from one cellular or organismal generation to another.
It is known that part of the genetic information is transmitted through the cytoplasm. But the information transmitted through the cytoplasm is also determined by genes. Therefore, in more in a broad sense Heredity can be understood as all mechanisms of information transmission over generations.
In animals that have nervous system, we are meeting special type purely functional continuity of adaptive reactions between generations, when the offspring, in imitation of their parents, develops the same conditioned reflexes that the parents acquired in individual life. This continuity is based on the mechanism conditioned reflex, and therefore it can be called signaling heredity. Signaling heredity arose in the process of evolution as a special mechanism for transmitting individual adaptation. These aspects of heredity are studied by a special direction in genetics - behavioral genetics. On signaling heredity in maternal behavior in mammals.
In livestock farming practice, the concept “ true heredity“combine nuclear and cytoplasmic inheritance. This is due to the fact that the characteristics of the body are controlled by the animals’ own genes. Along with the body’s own genes, the nature and degree of manifestation of certain traits in it can be influenced by genes localized in the DNA of pathogens (bacteria and viruses) and symbionts. This kind of heredity is called false. An example of false heredity can be the appearance of green body color in some worms as a result of the development of symbionts in their cells - single-celled green algae. In cases where heredity contains features of both true and false heredity and cannot be characterized unambiguously, it is called intermediate[Merkuryeva et al., 1991, p. 13].
So, heredity - this is the property of cells or organisms to transmit from generation to generation the ability to a certain type of metabolism and individual development, during which they form general signs and properties, as well as some individual characteristics of the parents.
1.1.1.2. Variability
In addition to the heredity of organisms, genetics studies their variability. Variability is the property of living organisms to acquire changes and exist in various options. From a genetic point of view, variability is the result of the reaction of the genotype to the influence of conditions external environment in the process of individual development of the organism.
Depending on the mechanism of occurrence and the nature of changes in characteristics, several types of variability are distinguished. First of all, we should highlight the variability hereditary And non-hereditary.
Non-hereditary (modification, paratypic ) variability reflects changes in phenotype under the influence of external factors. It occurs in animals and plants under the direct influence of the environment. Modifications are widespread in nature, since each organism is affected by various environmental factors during its development, and their action influences the formation of the characteristics of this organism. Even with the same heredity, individuals will differ somewhat from each other due to different living conditions.
Not all traits are equally susceptible to modification variability. For the most part When exposed to environmental influences, the size, weight, and productivity of animals change. Morphological characteristics are much more stable, especially species ones, which develop mainly under the influence of heredity, since environmental fluctuations within the boundaries of the conditions in which it can exist this type, these signs are not affected. Thus, by raising lambs under conditions of abundant feeding, it is possible to increase their weight and trim their wool, but it is impossible to change the nature of the coat. This is explained by the fact that the properties of the coat are very to a large extent determined by heredity.
Modification variability has a double meaning for agricultural practice. By creating certain conditions for developing organisms, it is possible to enhance the development of a desired trait or weaken an undesirable one. This is a positive feature of modifications for practice. However, the influence of the environment can smooth out hereditary differences between animals, with the result that the hereditarily better and worse individuals are identical in appearance or productivity. This prevents the correct selection of more valuable individuals for their hereditary qualities and slows down the improvement of breeds and varieties.
Hereditary , or genotypic variability , caused by the emergence of new genotypes, which leads to a change in phenotype. Hereditary variability is divided into two other types of variability - combinative And mutational. Mutational variability characterized by the sudden appearance in a single organism of any new features that its ancestors did not have. Mutations arise spasmodically as new ones qualitative changes. They are a consequence of structural changes in genes and chromosomes and are passed on to offspring. In the evolution of wild and domestic animals and plants, the significance of mutations is extremely great. Those features that distinguish domestic animals and cultivated plants from their wild ancestors arose as a result of mutational changes. Mutations that are valuable to humans are subject to artificial selection and thus spread and accumulate in a given species, creating differences between it and its wild ancestor. A striking example This can be confirmed by recently domesticated species of fur-bearing animals - mink and fox, which have relatively a short time living in cage conditions, a number of coat color mutations were discovered, representing great value for the fur industry.
The variability of organisms may be due to not only by gene mutation, but also combinations of various genes, new combinations of which lead to changes in certain characteristics and properties of the organism; this type of variability is called combinative variability
. These changes are also inherited. Combinative variability is usually observed in the offspring obtained as a result of crossing animals of different breeds and plants of different varieties, as well as in interspecific crossings. The sources of this variability are two parallel processes:
1) emergence of new gene combinations as a result of independent divergence of chromosomes in meiosis during the formation of gametes and their random association in zygotes and
2) emergence of new chromosome variants as a result of crossing over in the first meiotic division.
Combination variability plays an important role in agricultural practice. Using its laws, new breeds of animals and new varieties of plants are created. It is based on the improvement of existing breeds through the selection of pairs, the purpose of which is to obtain more valuable hereditary combinations and correct the shortcomings of one of the parents in the offspring with the positive qualities of the other.
Hereditary variability (both combinative and mutational), occurring in natural conditions under the influence of factors independent of humans, is called natural, or spontaneous . Variability arising under experimental conditions as a result of the use of forced crossing or various mutagenic factors, is called artificial, or induced variability . Induced combinative variability underlies practical selection in the creation of new plant varieties, animal breeds, and strains of microorganisms.
It is known that in each organism, in the process of individual development, regular changes in morphological and functional features. This variability is called ontogenetic . It is realized within the normal limits of the body’s reaction and, according to this criterion, should be classified as non-hereditary variability. However, the sequence and timing of these changes is determined by the genotype. For this reason, ontogenetic variability can be classified as hereditary [Inge-Vechtomov, 1989, p. 290]. Thus, ontogenetic variability has a dual nature.
The development of an organism is carried out as a single process under the influence of its heredity and environmental conditions. Therefore, a change in the development of any organ or tissue entails a change in the development of other organs and tissues physiologically or anatomically related to them. For example, changes in the functions of certain endocrine glands affect the development of certain groups of tissues or organs, or the entire growth of the body. Changes in the development of the heart will cause changes in blood circulation and, consequently, in the nutrition of organs and tissues. If a change in one characteristic is associated with a change in another, then such variability is called correlative. Depending on how one characteristic changes when another changes, correlative variability can be positive or negative (see the section “Statistical methods for studying variability”). Correlative variability is called positive when, with increased development of one trait, the other also intensifies, and negative, when increased development of one trait weakens the development of another.
It is known that it is almost impossible to combine in one breed, for example, cattle, very high milk productivity of animals with their high fattening ability. This is due to the fact that high milk content is due to intensive metabolism, and high meat qualities are due to reduced metabolism. For the same reason, the very high wool productivity of sheep, or the high egg production of chickens and a number of other characteristics cannot be combined with meat productivity. Sometimes, as a result of correlational variability, an organism develops some traits that increase its viability, and others that decrease it. Depending on the cumulative influence of such traits, an organism can be preserved by natural or artificial selection or, conversely, eliminated by it. Therefore, the correlative variability of traits limits the possibilities of using combinative variability in creating new breeds of animals and plant varieties. This forces geneticists to take it into account when conducting breeding work.
Modern study of heredity and variability is carried out on different levels organization of living matter: molecular, chromosomal, cellular, organismal and population. The variety of objects and methods of research in genetics was the reason for the emergence of a large number of its sections, such as cytogenetics, molecular, biochemical, radiation, medical and physiological genetics, as well as population genetics, ontogenetics (phenogenetics), etc.
1.1.2. Problems and tasks of genetics
To achieve the two goals outlined above, genetics will have to solve a number of important problems. Below will be listed only in the most general form the main problems studied by genetics. These problems are discussed in more detail in the relevant sections of the course.
In the vast majority of species of living beings, the material bridge connecting two generations is the male and female reproductive cells, which merge during fertilization. It is obvious that these two cells contain information in a certain way that determines the similarity of the offspring with their parents. At the same time, there is variability in organisms, as a result of which descendants usually differ to one degree or another from their parents and from each other. Thus, from one generation to another through the bridge formed by the germ cells, it is transmitted (albeit sometimes in a somewhat distorted form) information about all those diverse morphological, physiological and biochemical characteristics that should be realized in descendants. Based on this cybernetic nature of genetic processes, it is convenient in the following way formulate four main theoretical problems studied by genetics.
1.1.2.1. Theoretical problems genetics
Theoretical research in genetics covers a wide range of problems, which can be conditionally divided into 4 large groups.
1) Problems storage of genetic information. To solve these problems, geneticists study what material structures of the cell contain genetic information and how it is encoded in them.
2) Problems transmission of genetic information. The solution to these problems is associated with research into the mechanisms and patterns of transmission of genetic information from cell to cell and from generation to generation.
3) Problems implementation of genetic information. These problems arise from the need to understand how genetic information is translated into specific traits in a developing organism while being subject to various influences environment.
4) Problems changes in genetic information. To solve these problems, geneticists study the types and causes of changes to which genetic information is subjected, as well as the mechanisms of their occurrence [Gershenzon S.A., 1979].
All these four groups of genetic problems are studied at different levels of organization of living matter - molecular, cellular, organismal and population. The methods used in these studies vary depending on the level at which the research is being conducted.
1.1.2.2. Practical problems genetics
The conclusions obtained from the study of theoretical problems of heredity and variability serve as the basis for solving practical problems facing genetics, the main of which are listed below.
1) Selecting the Best Types of Crossing. Different types crossings (distant hybridization, unrelated crossings, related crossings of different degrees) have different effects on the hereditary properties of descendants. Knowledge of these differences and their genetic conditionality makes it possible to use in crop and livestock breeding such types of crosses that best correspond to the specific practical goal set in each case.
2) Choice of the most effective ways selection. Knowing how different ways selection influence hereditary traits, allows the use in plant growing and livestock breeding of those techniques that most quickly change necessary signs in the desired direction.
3) Controlling the development of hereditary traits. If we can understand the ways in which genetic information is realized in ontogenesis and the mechanisms of influence of environmental factors on these processes, then we will be able to select conditions that contribute to the formation of the most valuable traits in organisms and the suppression of undesirable ones. It has great importance to increase the productivity of cultivated plants and the productivity of domestic animals. This is also important for medicine, since it sometimes helps prevent the manifestation of human hereditary diseases, and in some cases even cure them.
4) Study of the mechanisms of mutagenesis and mutations. Knowledge of physical and chemical mutagens and the mechanism of their action makes it possible to artificially obtain new hereditarily altered forms. This makes it possible to obtain improved strains of beneficial microorganisms and varieties of agricultural plants and animal breeds. In medicine, knowledge of the laws of the mutation process is necessary to develop measures to protect human heredity from harmful mutagenic effects of the environment.
5) Genetic engineering– a section of practical genetics associated with the targeted creation of new genetic combinations of genetic material and its introduction into selected living organisms.
6) Study of private genetics cultivated plants, farm animals and humans. Although the main laws established by genetics are universal in nature, they are uniquely refracted in different organisms due to their specific differences, especially related to the biology of reproduction and the structure of the chromosomal apparatus. For practical purposes, you need to know which genes are involved in determining the beneficial or harmful traits of a given organism that are economically or medically important. Therefore, the study of the particular genetics of such traits is an obligatory element of practical genetic work [Gershenzon S.A., 1979].
To solve these problems, specific, specific tasks are formulated within each area of genetic research. We will get acquainted with some of them during the course.
1.1.2.3. Objectives of veterinary genetics
Text of the subsection "Problems of veterinary genetics".
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Veterinary genetics – this is the section general genetics, the subject of study of which is hereditary anomalies, diseases with a hereditary predisposition, the development of methods for the diagnosis and prevention of genetic abnormalities in animals, as well as the selection of animals for resistance to infectious diseases.
Veterinary genetics is closely related to general genetics. Theoretical achievements of general genetics very quickly find application in veterinary practice. However, these advances cannot be realized without a veterinarian. Therefore, the genetic education of veterinarians is necessary condition for diagnosis, treatment and prevention of hereditary diseases of domestic and farm animals. By using genetic knowledge a veterinarian can integrally (whole) understand all stages of an animal’s individual development as the fulfillment of the organism’s hereditary program in the process of ontogenesis under specific environmental conditions.Veterinary genetics sets itself the following tasks:
1) study of hereditary anomalies in animals;
2) development of methods for identifying heterozygous carriers of hereditary anomalies;
3) study of diseases with hereditary predisposition;
4) control of the spread of harmful genes in populations and their elimination;
5) study of the connection between cytogenetic disorders and hereditary diseases;
6) study of the genetics of immunity;
7) study of the genetics of pathogenicity and virulence of microorganisms and the interaction of microorganisms and macroorganisms;
8) development of methods for early detection of resistance and susceptibility of animals to diseases;
9) study of the environmental impact harmful substances on the hereditary apparatus of animals;
10) study of genetically determined reactions of animals to drugs;
11) creation of herds, lines, types, breeds that are resistant to diseases, with a low level of genetic load and well adapted to certain environmental conditions;
12) the use of biotechnology methods to increase the resistance of animals to diseases [Petukhov V.L. et al., 1996, p. 4].
1.2. Genetics methods
Modern genetics studies the phenomena of heredity and variability at various levels of organization of biosystems - from molecular to population and species. At the same time, genetics is based on the achievements various industries biology - biochemistry, biophysics, microbiology, cytology, embryology, zoology, botany, plant growing and animal husbandry. Therefore, depending on the specific task facing the geneticist researcher, he may use methods of molecular biology and biochemistry, microbiological and cytological methods, methods of embryology, or methods of population biology. We will become familiar with many specific research methods during the course. But all of them can be combined into several groups common methods by similarity methodological approach to the study of heredity and variability.1.2.1. Hybridological method
Hybridological analysis method consists in crossing organisms and subsequent taking into account the splitting of characteristics. In its completed form, this method was proposed by G. Mendel and to this day is one of the main methods of genetic research
Gregor Mendel formulated rules of hybridological analysis which all geneticists follow:
1. The organisms to be crossed must belong to the same species.
2. Crossed organisms must be clearly distinguishable according to individual characteristics.
3. The characteristics being studied must be constant, i.e. reproduce from generation to generation when crossed within a line.
4. It is necessary to characterize and quantitatively account for all classes of segregation if it is observed in hybrids of the first and subsequent generations.
Thus, the method includes a system of crosses of pre-selected parental individuals differing in one, two or three alternative characters, the inheritance of which is studied. A thorough analysis of hybrids of the first, second, third, and sometimes subsequent generations is carried out according to the degree and nature of the manifestation of the studied characteristics.
This method is of great importance for the breeding of plants and animals. It also includes the so-called recombination method, which is based on the phenomenon of crossing over - the exchange of identical regions in the chromatids of homologous chromosomes in prophase I of meiosis. This method is widely used to compile genetic maps, as well as for creating recombinant DNA molecules containing genetic systems various organisms.
1.2.2. Genealogical method
Genealogical method is a method of studying the inheritance of characteristics by offspring from ancestors among generations of organisms of the same family (or genus). The genealogical method is one of the variants of the hybridological method. The method is based on an analysis of the distribution of normal or pathological characteristics in a number of generations, indicating family ties between members of a family tree. It is used in the study of the inheritance of traits by analyzing pedigrees, taking into account their manifestation in organisms of related groups (humans or animals) in several generations.
The genealogical method is one of the most universal methods in genetics. This method is used in the study of heredity in humans and animals in which infertility is genetically determined. The genealogical method allows one to overcome the difficulties arising due to the impossibility of directed crosses (for example, in humans) or the low fertility of organisms (for example, in horses).
1.2.3. Twin method
Among animals it is very difficult to find two individuals with the same heredity. Only some twins have identical heredity. Gemini two or more offspring born at the same time by the same mother in usually singleton animals and humans are called[Reimers, 1988]. There are two types of twins - monozygotic And dizygotic.
Dizygotic (fraternal, non-identical) twins arise from separately fertilized two or more eggs that mature at the same time.Monozygotic (identical) twins - these are twins of the same sex, developed from one fertilized egg as a result of its division after the first division into two independent cells, giving rise to two organisms. Monozygotic twins are born, although rarely, in cattle, sheep, and pigs. Birth frequency in humans, according to various sources:– 10 per 1000, among them 25% are monozygotic twins [Dubinin, 1985];
– 10 out of 840, among them 33% are monozygotic twins [Slyusarev, Zhukova, 1995].
Rice. Identical twin Ayrshire heifers Sandy and Candy, born in New York State [Hutt, 1969].
All monozygotic twins have almost the same genotype. Such twins are very similar in their characteristics (Fig.), and the small differences observed in them are caused solely by the influence of environmental conditions. Therefore, they represent a very convenient object for studying the influence of heredity and environment on the development of a particular trait. For example, to study the influence of feeding conditions on the growth and development of identical twins in cattle, special experiments were carried out. The heifers - 9 pairs of identical twins - were divided into two groups - one heifer from a twin in each group. Heifers of one group were fed intensively from birth - 33% above the norm, while heifers of the other group were fed sparingly - 33% below the norm. Similarly, two more groups of 8 heifers each were created; in one group the diet was 25% higher, in the other - 25% lower than normal. The results of the experiment showed that heifers that received abundant feeding significantly exceeded the weight of their twin sisters that received poor feeding. However, the same conditions influenced their height growth to a lesser extent, since there were no differences in height among the animals of the three groups; only a group of heifers, whose diets were 33% below the norm, lagged behind the animals of all other groups in this indicator. Consequently, the same environmental conditions have different effects on the development of various traits.
So, the similarity or difference in the genotypes of twins makes it possible to use the twin method in studying the influence of certain environmental factors on the genotype of an individual, as well as to identify the relative role of genotypic and modification variability in the overall variability of a trait.
1.2.4. Cytogenetic method
Cytology methods are used to study the cell as the basic unit of living matter. The field of genetics that studies the structure and function of chromosomes is calledcytogenetics . Cytogenetic methods are designed to study the structure of individual chromosomes and chromosome sets as a whole. The most common method in cytogenetics is light microscopy. The object of cytogenetic studies can be somatic and generative cells, both interphase and in a state of division. Analysis of chromosome conjugation in meiosis and observation of exchanges between homologous and non-homologous chromosomes deepen our knowledge of the material carriers of heredity.
For detailed analysis chromosomes use various methods of total (monochrome, solid) and differential coloring of chromosomes. Moreover, thanks to success in molecular genetics designed fundamentally new method studying chromosomes - molecular hybridization method in situ(FISH method; see section “Cytological bases of heredity”).
1.2.5. Somatic cell hybridization method
At the end of the 50s of the last century, experimental biologists developed methods for cultivating (growing) cells outside the body in nutrient media. The somatic cells of the body contain all the genetic information. This makes it possible to study issues of animal and human genetics that are difficult or even impossible to study on the whole organism. Such studies are possible because metabolic processes can be isolated from a complex chain of interconnected reactions occurring in the body.
In 1960, the French biologist J. Barsky proved that when cells from two different lines of mice are co-cultivated in a nutrient medium, these cells can merge, forming hybrids containing sets of chromosomes from both parental forms. Later, hybrids were obtained between cells belonging to different species (for example, human - mouse). Most hybrid cells die, but some of them, containing two nuclei, can continue to develop and multiply by division. In such hybrid cells, very interesting processes, caused by the work of two genomes at once. Studying these processes allows you to:
a) study the mechanisms of gene action,
b) determine the mutagenicity of chemical and physical factors,
c) more accurately diagnose hereditary diseases at the biochemical level in adult organisms and even before birth - in embryos.
1.2.6. Mutation method
The mutation method (mutagenesis analysis) allows us to establish the nature of the influence of mutagenic factors on the genetic apparatus of the cell, DNA, chromosomes, and on changes in the characteristics or properties of organisms. Mutagenesis is used in microbiology to create new strains of bacteria, in the breeding of farm animals and plants - to create source material for selection.
1.2.7. Biochemical method
Biochemical methods have been used in the study of animal and human genetics since the beginning of the twentieth century. Biochemical indicators (for example, the primary protein product of a gene or the accumulation of pathological metabolites inside the cell or in extracellular fluid) characterize the disease better than its clinical symptoms. The importance of biochemical methods increased as hereditary diseases were studied and biochemical methods were improved.
Biochemical methods are aimed at identifying the biochemical phenotype of an organism. Objects of biochemical diagnostics can be urine, sweat, plasma and serum, blood cells, cell cultures. Phenotype analysis can be performed at different levels, from the primary gene product (polypeptide chain) to the final metabolites.
1.2.8. Molecular genetic method
The main objects of genetic research at the molecular level are nucleic acid molecules - DNA and RNA, which ensure the preservation, transmission and implementation of hereditary information. The study of nucleic acids of viruses, bacteria, fungi, plant and animal cells cultivated outside the body makes it possible to establish the patterns of gene action during the life of the cell and organism.
1.2.9. Ontogenetic (phenogenetic) method
The ontogenetic (phenogenetic) method allows us to establish the degree of influence of genes and environmental conditions on the development of the studied properties and characteristics in the process of individual development of the organism (ontogenesis). Changing the conditions of keeping and feeding animals affects the nature of the manifestation of hereditarily determined traits and properties in ontogenesis.
1.2.10. Population method
The population method is used to study the phenomena of heredity in populations. This method makes it possible to establish the frequency of dominant and recessive alleles that determine a particular trait, the frequency of dominant and recessive homozygotes and heterozygotes, the dynamics of the genetic structure of populations under the influence of mutations, isolation and selection. The method is theoretical basis modern animal breeding.
When performing population genetic studies, scientists can use any other genetic methods available to them, for example, cytogenetic, biochemical, molecular genetics. Examples of the use of molecular genetic methods in population genetic studies include the establishment
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A new molecular genetic study confirming that North American Indians have Altai roots was carried out by a group of anthropologists from the University of Pennsylvania and scientists from the Laboratory of Population Ethnogenetics of the Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences. The study results were published on January 26, 2012 in the American Journal of Human Genetics. Anthropologists set themselves the goal of finding out from which nationality the indigenous inhabitants of the American continent descended and determining genetic markers, common to Altaians and North American Indians
DNA analysis of various nationalities inhabiting Altai and the indigenous population North America, carried out using modern genetic methods, allowed scientists to clarify the issue of Altai’s connection with North America, who exactly inhabited it and when this happened.
According to Theodore Schurr, professor of anthropology at the University of Pennsylvania, Altai is “a key point, a place where people have come and gone for thousands and thousands of years.”
Analyzing the genetic data of the indigenous Altaians, scientists looked for markers in their mitochondrial DNA. The study of the mitochondrial genome is the main tool for identifying people. The possibility of such identification is due to the group and even group patterns existing in the human mitochondrial genome. individual differences which are inherited through the maternal line. The authors of the work compared these DNA samples with those obtained from Indians, residents of Southern Siberia, Central and East Asia, and Mongolia. In the inhabitants of Southern Altai, they discovered a mutation characteristic of North American Indian women.
DNA studies have shown that the genetic markers of the indigenous population of North America and the indigenous population of the Altai Territory are identical. Approximately 15-25 thousand years ago, these prehistoric people from Altai began to spread throughout northern regions Siberia and eventually reached America. Then these people crossed the ice from Russia to America. Thus, from Altai Territory descends from the ancestors of the first American Indians.
Scientists have calculated the time when the Altai and Indian lines separated and each went their own way, accumulating their own mutations, unlike each other, in their genomes. This happened 13-14 thousand years ago. Scientists also found that, most likely, the settlement of the North American continent occurred in several waves, separated from each other in time.
Previously conducted ethnographic studies showed that the peoples of Northern Altai are very different from the peoples of the South. The former, in terms of language and cultural traditions, gravitate towards the Ural peoples, such as the Samoyeds (Samoyeds). Southerners, on the contrary, show close ties with the Mongols, Uighurs and Buryats. However, judging by the results of genetic studies of mitochondrial DNA, then, despite all their cultural and linguistic differences, the peoples of Northern and Southern Altai are, albeit distant, but still relatives on the maternal side. And, according to Professor T. Schurr, the main “bridge” connecting northerners and southerners was women.
See also
1.2.11. Biometric method
An integral part of each of the above methods is statistical analysis– biometric method. The very birth of genetics as an exact science became possible thanks to the use of mathematical methods in the analysis of biological phenomena. G. Mendel applied quantitative approach to study the results of crossings and construct hypotheses that explain the results obtained. Since then, methods of biological statistics (biometrics) have become an integral part of genetic analysis. It represents a series of mathematical techniques that make it possible to determine the degree of reliability of the data obtained, to establish the likelihood of differences between the indicators of experienced and control groups animals. The biometric method is indispensable in the study of the inheritance of quantitative traits, as well as in the study of variability, especially non-hereditary, or modification.
1.2.12. Mathematical modeling method
In genetics, the method of modeling various molecular structures And genetic processes using computers (see, for example,). With the help of such models, the inheritance of quantitative traits in populations is studied, and the potential effectiveness of selection methods - mass selection, selection of animals according to selection indices - is assessed. Basics of the method mathematical modeling in genetics are set out in the book “Fundamentals of Mathematical Genetics”. Particularly wide application this method found in the area genetic engineering And
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A book on the basics of mathematical modeling in molecular biology.
Setubal J., Meidanis J. Introduction to computational molecular biology. -Moscow-Izhevsk, Publishing house: Scientific Research Center "Regular and Chaotic Dynamics", Institute of Computer Research, 2007. - 420 p.
The book is an introduction to computational molecular biology, describes its most typical problems and proposes effective algorithms for solving them. The book begins with a review of the fundamental concepts of molecular biology (the structure and functions of proteins and nucleic acids, mechanisms of molecular genetics), then introduces the most important mathematical objects, such as graphs and lines, and are given general information about algorithms. All this sets the stage for understanding further sections of the book: comparing sequences (and searching in the database), assembling DNA fragments, compiling physical cards DNA, phylogenetic trees, gene rearrangement, macromolecule structure prediction, and computation using DNA. Each of these sections contains a discussion of biological background, definitions of key terms, Full description applied mathematical or computer models, as well as examples of algorithm implementations.
The book is intended for programmers, mathematicians and biologists seeking to expand their knowledge of this exciting new field of science, where there are still so many unsolved problems.
Genetics actively uses other methods of related natural sciences. Methods of chemistry and biochemistry are used for a more detailed characterization of inherited metabolic traits and to study the properties of protein molecules and nucleic acids. For the same purposes, methods of immunology and immunochemistry are used, which make it possible to identify very specifically even minute quantities of certain gene products, primarily proteins.
Genetics widely uses methods of physics: optical, sedimentation, methods of labeled atoms for marking and identifying various classes of macromolecules. The most widely used physical, chemical and physicochemical methods are used in molecular genetics and genetic engineering.
Geneticists working with various objects cannot do without the methods of zoology, botany, microbiology and other disciplines. At the same time, the use of modern genetic methods to study evolutionary process increases the importance of genetics itself for comparative method, used by microbiologists, botanists and zoologists.
Genetic methods Research has significantly enriched the theoretical fields of biology, medicine, as well as animal science, veterinary medicine, breeding and breeding of farm animals, as well as plant breeding and seed production.
1.3. History of the development of genetics
Genetics is one of the youngest biological sciences. She is just over 100 years old. However, during this relatively short period, genetics not only turned into an independent scientific discipline, but served as the foundation for the creation of some others important sciences, such as molecular biology and genetic engineering.1.3.1. Prerequisites for the emergence of genetics
Attempts to understand the nature of the transmission of traits by inheritance from parents to children were made in ancient times. Reflections on this topic are found in the writings of Hippocrates, Aristotle and other thinkers.
IN XVII-XVIII centuries Scientists began to try to understand the process of fertilization and look for which principle - male or female - is associated with the secret of the development of a new organism. During this period, debate about the nature of heredity resumed with new strength. In 1694, the German botanist Rudolf Cammerarius (1665-1721) discovered that pollination was necessary for fruit set. Thus to end of XVII V. The scientific ground was prepared for the start of experiments on plant hybridization. The first successes in this direction were achieved at the beginning of the 18th century.
The first interspecific hybrid was obtained by the Englishman T. Fairchild by crossing carnations. In 1760 German botanist Joseph Kölreuter (1733-1806) was the first to carefully consider experiments to study the transmission of traits when crossing plants. In 1761-1766. J. Kölreuter, in experiments with tobacco and cloves, showed that after the transfer of pollen from one plant to the pistil of a plant that differs in its morphological characteristics, ovaries and seeds are formed, producing plants with properties intermediate in relation to both parents. The precise method developed by J. Kölreuter led to rapid progress in the study of the hereditary transmission of traits.
Rice. Thomas Andrew Knight (1759-1839).
At the end XVIII-early XIX V. English plant breeder Thomas Andrew Knight (fig.), while crossing different varieties of peas, made an important observation - he discovered indivisibility of small characters in various crosses. The discreteness of hereditary material, proclaimed in ancient times, received the first scientific basis. T. Knight is credited with the discovery of “elementary hereditary characteristics.”
Further significant advances in the development of crossbreeding methods are associated with French plant breeders Augustin Sajray (1763-1851) and Charles Naudin (fig.).
Rice. Charles Naudin (1815-1899).
The greatest achievement of O. Sazhre was the discovery of the phenomenon of dominance. When crossing varieties of vegetable crops, he often observed the suppression of the trait of one parent by the trait of the other. This phenomenon manifests itself to the maximum extent in the first generation after crossing, and then the suppressed traits were again revealed in some of the descendants of the next generation. Thus, O. Sazhre confirmed that elementary hereditary characteristics do not disappear during crossing. C. Naudin also came to this conclusion in 1852-1869. But C. Naudin went even further, starting a quantitative study of the recombination of hereditary inclinations during crossings. However, disappointment awaited him along this path. Incorrect methodical technique- simultaneous study of a large number of signs - led to great confusion in the results, and he was forced to abandon his experiments. The shortcomings inherent in the experiments of C. Naudin and his predecessors were eliminated in the works of G. Mendel.
The idea of differentiating divisions of the cell nucleus of a developing embryo was first expressed in 1883 by the German embryologist Wilhelm Roux (1850-1924). V. Roux's conclusions served as the starting point for the creation of the theory of germ plasm, which received its final form in 1892, when the German zoologist August Weismann clearly pointed out the carriers of hereditary factors - chromosomes.
Row most important discoveries, committed in the 19th century, were a prerequisite for the emergence of scientific genetics at the turn of the 20th century. These discoveries should include the creation of the theory of evolution and the creation of the cellular theory.
Rice. The first edition of Charles Darwin’s book “The Origin of Species by Means of Natural Selection.”
The greatest achievement of natural science in the 19th century was the creation of evolutionary theory. In 1859, Charles Darwin in “The Origin of Species” established the principle evolutionary development organisms and showed that the factors of evolution are natural selection, heredity and variability. Charles Darwin's theory quickly gained wide recognition among scientists. Scientists understood that evolution is possible only on the basis of the occurrence of changes in living beings and the preservation of these changes in their descendants. Therefore, the evolutionary teachings of Charles Darwin increased interest in the problems of heredity and variability in the second half of the 19th century.
At that time, scientists proposed several hypotheses about the alleged mechanism of heredity. Although these hypotheses were more perfect than the hypotheses proposed earlier, they were also largely speculative. Subsequent experimental work showed them to be wrong. At the same time, some of these rejected hypotheses contained provisions that were later confirmed. Consequently, they played their positive role in the development of ideas about heredity and variability. Therefore, let us consider three of these hypotheses that deserve the most attention.
The most fundamental speculative hypothesis was the “temporary hypothesis of pangenesis” by Charles Darwin, set out in the last chapter of his “Changes in Domestic Animals and Cultivated Plants” (1868). According to his ideas, in each cell of any organism, special particles are formed in large numbers - gemmules, which have the ability to spread throughout the body and collect in cells serving for sexual or vegetative reproduction. Darwin assumed that the gemmules of individual cells could change during the ontogeny of each individual and give rise to modified descendants. Darwin's assumption about the inheritance of acquired characteristics was experimentally refuted by F. Galton (1871).
Another speculative hypothesis about the nature of heredity was proposed by the German botanist Karl Naegeli (1817-1891) in his work “Mechanical and Physiological Theory of Evolution” (1884). K. Negeli suggested that hereditary inclinations are transmitted only by part of the cell substance, which he called idioplasm. The rest of the cell (stereoplasm), according to his idea, does not bear hereditary characteristics. He suggested that idioplasm consists of molecules connected to each other into large thread-like structures - micelles, grouped in bundles and forming a network that permeates all the cells of the body. K. Nägeli's hypothesis prepared biologists for the idea of the structuring of the material carriers of heredity.
Rice. August Weismann (1834–1914).
The most detailed was the third hypothesis, proposed by the German zoologist August Weismann (Fig.). Developing the idea of unequal hereditary division, A. Weisman logically came to the conclusion that there are two clearly demarcated cell lines in the body - germinal and somatic. Germline cells provide continuous transmission of hereditary information, are “potentially immortal” and are capable of giving rise to a new organism. Somatic cells do not have such properties. This separation of two categories of cells was important for the subsequent development of genetics. August Weismann believed that germ cells contain a special substance - the carrier of heredity (“germ plasm”) and identified this substance with the chromosomes of the cell nucleus.
First, V. Roux in 1883, and then A. Weisman, suggested the linear arrangement of hereditary factors in chromosomes and their longitudinal splitting during mitosis, which largely anticipated the future chromosome theory heredity.
A. Weisman's assumption about the leading role of chromosomes in the transmission of hereditary properties was correct. Two more elements of his hypothesis were also true: 1) a statement about the great importance of crossings as the cause of variability that provides material for evolution, and 2) the denial of the inheritance of acquired characteristics, that is, bodily changes caused by external influences during the life of an organism. But along with these correct provisions, Weismann’s hypothesis contained many erroneous provisions. (Erroneous positions may include his ideas about the structure of the chromosomes of germ cells, about their breakdown into special rudiments (“determinants”), which then enter different cells of the body and determine the properties of these cells, about “rudimentary selection” that regulates the distribution of such determinants between cells, about the absence of "germ plasm" in the cells of the body. All these parts of Weismann's hypothesis were not based on facts, were speculative in nature and were refuted by later research).
In the second half of the 19th century, intensive research into the structure of the cell took place. The first idea of a cell as an elementary component of an organism was given by Robert Hooke back in 1665. However, only in the first half of the 19th century (in 1838) M. Schleiden and T. Schwann created the theory cellular structure. And in the last three decades of the 19th century, a series of discoveries established the role of the cell in heredity and development. It has been shown that the essential components of a cell are the nucleus and cytoplasm. R. Virchow put forward the fundamental concept according to which any cell comes only from a cell. This established the idea of the continuity of life, showing that it is based on cell division. In 1874 I.D. Chistyakov, and a year later E. Strasburger established that cell division is associated with complex processes maintaining the number of chromosomes in daughter cells. This process is carried out in the form of indirect division of the nucleus, which in 1889 W. Flemming called mitosis. He showed that during mitosis, each chromosome splits longitudinally, forming two daughter chromosomes. In 1875, O. Hertwig established the essence of fertilization. Studying the process of fertilization in a sea urchin, he showed the role of the nuclei of female and male gametes, which, after penetration of the sperm into the egg, merge into the common nucleus of the zygote. Soon the same phenomenon was discovered by N.N. Gorozhankin in gymnosperms and G. Strasburger - in angiosperms.
While studying the behavior of chromosomes in cells that form gametes, E. Van Beneden and T. Boveri discovered the phenomenon of meiosis. They found that during meiosis, the process of reduction (decrease) in the number of chromosomes by half occurs. After the fusion of germ cells with a halved number of chromosomes, their number in the zygote nucleus is restored to the normal level. In 1896, E. Wilson’s book “The Role of the Cell in Heredity and Development” was published. She was a synthesis achievements XIX century in the area cell theory. Its main content was evidence of the fact that chromosomes are the physical carriers of heredity.
Individual differences, even between closely related organisms, are not necessarily due to differences in the genetic structure of these individuals. Such differences may be caused by different living conditions of the compared individuals. Therefore, conclusions about genetic differences can only be made based on analysis large number individuals. The first to draw attention to mathematical patterns in individual variability was the Belgian mathematician and anthropologist A. Catlet. He was one of the founders of statistics and probability theory.
At that time, the question of the possibility of inheriting deviations from the average quantitative characteristic of a trait observed in individual individuals was very acute. Various researchers have analyzed this issue. The work of the English anthropologist Francis Galton (1882-1911), who collected data on the inheritance of height in humans, was very serious. Then F. Galton studied the inheritance of the size of the flower corolla in sweet peas and came to the conclusion that only a small part of the deviations observed in the parents are transmitted to the offspring. F. Galton tried to give his observation a mathematical expression, initiating large series works on statistical analysis of inheritance.
Follower of F. Galton English biologist and the mathematician Karl Pearson (1857-1936) continued this work on a larger scale. In this area, the most serious research was carried out in 1903-1909. Danish biologist Wilhelm Johansen (1857-1927). He paid main attention to the study of genetically homogeneous material. Based on the results obtained, Johansen gave precise definition concepts of “genotype” and “phenotype” and laid the foundations modern understanding the role of individual variability.
None of the scientists of that time were able to discover the laws of inheritance. However, the very approach to the problem of inheritance by studying the offspring of crossing individuals with different characteristics and analyzing the distribution of these characteristics among the descendants was absolutely correct. It was he who prepared the ground for the emergence of genetics as a science.
1.3.2. Main stages of development of genetics
The honor of discovering quantitative patterns accompanying the formation of hybrids belongs to the Czech botanist Johann Gregor Mendel (Fig. 1.5). In the works he carried out in 1856-1863, he revealed the foundations of the laws of heredity. These patterns subsequently formed the basis of genetics.
Rice. Johann Gregor Mendel (1822-1884).
Initially, G. Mendel paid attention to the choice of object. He chose peas for his research. The basis for this choice was, firstly, that peas are a strict self-pollinator, and this sharply reduced the possibility of introducing unwanted pollen; secondly, at that time there were a sufficient number of pea varieties that differed in several inherited traits.
G. Mendel received 34 varieties of peas from various farms. After testing for two years whether they retained their characteristics unchanged when propagated without crossing, he selected 22 varieties for experiments.
G. Mendel began with experiments on crossing pea varieties that differed in one trait (monohybrid crossing). In all experiments with 7 pairs of varieties, the phenomenon of dominance in the first generation of hybrids, discovered by O. Sajre and C. Naudin, was confirmed. G. Mendel introduced the concept of dominant and recessive traits. He called the traits that are transformed into hybrid plants completely unchanged as dominant. or almost unchanged. He designated recessive traits that become hidden during hybridization. Then G. Mendel for the first time managed to give quantification frequencies of occurrence of recessive forms among total number offspring from crossings.
To further analyze the nature of heredity, G. Mendel studied several more generations of hybrids crossed with each other. As a result of his work, the following generalizations received a solid scientific basis:
1. The phenomenon of unequal hereditary characteristics.
2. The phenomenon of splitting the characteristics of hybrid organisms as a result of their subsequent crossings. Quantitative patterns of splitting were established.
3. Detection of not only quantitative patterns of splitting according to external, morphological characteristics, but also the determination of the ratio of dominant and recessive inclinations among forms that in appearance are not different from dominant ones, but are mixed in nature.
Thus, G. Mendel came close to the problem of the connection between hereditary inclinations and the characteristics they determine. Due to the recombination of inclinations (later V. Johansen called these inclinations genes), during crossing, zygotes are formed that carry a new combination of inclinations, which determines the differences between individuals. This position formed the basis of a fundamental law - the law of gamete purity.
Experimental studies and theoretical analysis of the results of crossings carried out by Mendel were ahead of the development of biology by more than a quarter of a century. In 1865, G. Mendel reported the results of his research at a meeting of the Brno Society of Naturalists and later published them in the Proceedings of this society. However, this work of G. Mendel did not attract the attention of his contemporaries. She remained forgotten for 35 years.
Rice. Hugo De Vries (1848-1935).
The date of birth of genetics is considered to be 1900., when, independently of each other, three botanists repeated the discovery of G. Mendel. They were Hugo De Vries (in Holland), who conducted experiments with poppy and other plants, Karl Erich Correns (in Germany), who studied the segregation of traits in corn, and Erich von Tschermak (in Austria) who analyzed the inheritance of traits in peas.
Rice. Karl Erich Correns (1864-1833).
By comparing their results with those of other scientists, these researchers discovered Mendel's forgotten work. They were amazed at the similarity of G. Mendel's results with the results obtained by them. These researchers highly appreciated the depth and significance of the conclusions made by G. Mendel. Therefore, when publishing their data, they specifically emphasized that their results fully confirm the conclusions made by G. Mendel.
Rice. Erich von Tschermak (1871-1962).
Since 1900, genetics has gone through a number of stages of development. Each of them was characterized by the prevailing research directions at that time. All stages of the development of science are closely interconnected, since the transition from one stage to the next became possible thanks to the discoveries made at the previous stage. At the same time, at each new stage, along with the development of new directions, research into the problems posed in the previous stages continued. Therefore, the boundaries between the stages of genetic development are arbitrary. With this caveat, the history of genetics is divided into five main stages [Dubinin N.P., 1985].
Five stages in the history of genetic development:
- the first stage – from 1900 to 1910;
- second stage – from 1910 to 1920;
- third stage - from 1920 to 1940;
- fourth stage - from 1940 to 1953;
- fifth stage – from 1953 to the present.
S.M. Gershenzon outlines the boundaries of these periods somewhat differently: 1900-1912, 1912-1925, 1925-1940, 1940-1955. and from 1955 to the present.
1.3.2.1. The first stage of development of genetics (1900-1910)
After the rediscovery of Mendel's laws, the era of classical genetics began. The first period is characterized by the intensive development of Mendelism, confirmation of the laws of heredity discovered by G. Mendel with ever new hybridological experiments carried out in different countries ah on various plants and animals. As a result of these experiments, it became clear that the laws established by G. Mendel are universal.Rice. William Batson (1861-1926).
Over the years, genetics has emerged as an independent biological science and received wide recognition. The name “genetics” (from the Latin word geneo - I generate) was proposed for this young science in 1905 by the English scientist William Bateson (fig.). A little later, such important genetic concepts, as a gene, genotype, phenotype. These terms were proposed in 1909 by the Danish geneticist Wilhelm Ludwig Johansen (Fig.).
Rice. Wilhelm Ludwig Johansen (1857-1927).
During these same years, some new ones were born important directions genetic research, which will develop only in subsequent periods. These directions should include the synthesis that had emerged by this time of the accumulated information about the chromosomes of the cell nucleus, mitosis and meiosis, on the one hand, and genetic data, on the other. Already in 1902, two scientists - T. Boveri in Germany and V. Setton in the USA - simultaneously drew attention to the parallelism in the behavior of chromosomes during meiosis and fertilization with the inheritance of traits according to Mendel’s laws, which served as a prerequisite for the creation of the chromosome theory of heredity.
In 1903, the work of V. Johansen “Inheritance in populations and pure lines” appeared. By self-pollinating beans in lines, each of which came from one original plant, V. Johansen obtained the so-called pure lines. All individuals in such lines had the same hereditary content. However, growing in beds under the influence various factors environment, they turned out to be different in grain weight, height and other characteristics. Receiving offspring from extreme options, V. Johansen was convinced that these deviations were not passed on to descendants; they all turned out to be non-inherited modifications. Based on the facts obtained, he clearly separated the hereditary factors that determine this or that characteristic or property from these characteristics and properties themselves.
On this same initial stage development of genetics revealed that there are traits whose inheritance does not comply with Mendel's laws. Thus, the English geneticists William Batson (Fig. 1.9) and Reginald Punnett in 1906, in experiments with sweet peas, discovered the phenomenon of linked inheritance of traits. Another English geneticist L. Doncaster in the same 1906, in experiments with the gooseberry moth butterfly, discovered sex-linked inheritance. In both cases, the hereditary transmission of characteristics of the crossed forms clearly did not occur as required by Mendel's laws. Number various examples In both of these types of deviations from Mendelian inheritance then began to accumulate rapidly. Later it was established that there is no contradiction with Mendelism in these deviations. These apparent contradictions are eliminated by the chromosomal theory of heredity.
Already at the first stage of the development of genetics, primarily thanks to the work of V. Bateson with chickens, rabbits and mice, it became clear that the genotype is not a set of individual genes independent in their action. It was shown that genes are mutually dependent in their action and that the development of any trait is associated with the action of a number of genes. At the same time, the features of development also depend on environmental conditions. The characteristics of an organism, its phenotype, are the result of the interaction of heredity and environment.
The successful development of genetics was facilitated by the substantiation of the mutation theory. In 1899, Russian botanist, professor at Tomsk University S.I. Korzhinsky published the monograph “Heterogenesis and Evolution.” In it, he gave a number of examples of hereditary variability of traits in plants and expressed the idea that the reason for the appearance of new hereditary properties can only be single changes in the internal principles of heredity. Around the same time (1901), the Dutchman Hugo de Vries discovered plants with single hereditary deviations in his evening primrose crops. He substantiated the theory of mutations, according to which new hereditary characteristics arise as a result of sudden changes in discrete units included in the material basis of heredity. To denote cases of the appearance of hereditary deviations, G. de Vries introduced the term “mutation”.
In 1909, K. Correns published a paper on the inheritance of a number of characteristics through plastids. This research became the source of the study of extranuclear, or cytoplasmic, inheritance. Since the laws of transmission of plastids and other cytoplasmic elements carrying DNA molecules differ from the Mendelian laws of chromosome transmission, they are called non-Mendelian heredity.
At this initial stage of the development of genetics, the first attempts appeared to explain the patterns of evolution from a genetic perspective. In 1908, G. Hardy and V. Weinberg showed that Mendelian laws explain the processes of gene distribution in populations.
In 1909, A. Garrod discovered that in humans the disease alkaptonuria is an inborn error of metabolism. This discovery was the origin of biochemical genetics.
1.3.2.2. The second stage of development of genetics (1910-1920)
Home distinctive feature The second stage in the development of genetics was the creation and approval of the chromosomal theory of heredity. The leading role in the creation of this theory belongs to the experimental work of the American geneticist Thomas Gent Morgan (Fig.) and three of his students - Alfred Sturtevant (1871-1970), Calvin Bridges (1889-1938) and Hermann Möller (1890-1967). In these experiments conducted on Drosophila, it was shown that the hereditary inclinations - genes - lie in the chromosomes of the cell nucleus and that the transmission of hereditary characteristics is determined by the fate of the chromosomes during the maturation of germ cells and fertilization.
Rice. Thomas Gent Morgan (1861-1945).
The genetic work of T. Morgan's school helped to understand the structure of chromosomes much more deeply than cytological studies alone allowed. T. Morgan's employees learned to build chromosome maps indicating the exact location of different genes on them. The first such map was compiled by A. Sturtevant for one of the Drosophila chromosomes. Based on the chromosomal theory of heredity, it was proven chromosomal mechanism gender determination. The main role in this was played by the works of T. Morgan and the American cytologist E. Wilson. At the same time, other work on the genetics of sex began. The research of the German geneticist R. Goldschmidt was of particular importance in this area.
The chromosomal theory of heredity was biggest achievement biology. All further development of genetics took place in the light of this theory. In addition, the chromosome theory has had strong influence on cytology, embryology, biochemistry, evolutionary theory. Later it served as one of the prerequisites for the emergence and development of modern molecular biology. During this period, genetic research began quantitative characteristics. In the works of G. Nilsson-Ehle, E. East and others, it was established that the inheritance of quantitative traits also obeys Mendel’s laws.
At the second stage of the formation of genetics, some genetic areas important for agriculture began to develop rapidly. Among them are works on elucidating the nature of heterosis, on comparative genetics cultivated plants, on interspecific hybridization of fruit plants. Research into private genetics was actively conducted different types cultivated plants and domestic animals. The results of these studies were of great importance for the development of the genetic basis of selection, seed production and breeding.
Rice. Nikolai Konstantinovich Koltsov (1872-1940).
The (second) period under consideration includes the formation of genetics in our country. In the twenties of the last century, three genetic schools emerged in Russia, headed by prominent scientists - Nikolai Konstantinovich Koltsov (Fig.), Yuri Aleksandrovich Filipchenko (Fig.) and Nikolai Ivanovich Vavilov (Fig.). These schools played an important role in the widespread development of research in general and applied genetics in Russia. Nikolai Konstantinovich Koltsov first used physical methods research in the study of living cells. He was the first to organize genetic research in Russia (Soviet Union, 1921) and for the first time raised in his works (1927-1935) a number of problems that now form the basis of molecular genetics. He outlined the problems of the structure and functioning of subcellular structures, the structure of chromosomes, the nature and nature of the mutation process, etc. N.K. Koltsov has a hypothesis according to which chromosomes are giant hereditary molecules, the links of which are genes.
Rice. Yuri Alexandrovich Filipchenko (1882-1930).
Rice. Nikolai Ivanovich Vavilov (1887-1943).
Koltsov in Moscow, Filipchenko and Vavilov in St. Petersburg attracted a number of outstanding biologists to collaborate. IN short term Fruitful scientific work was established on many problems of genetics, the promotion of genetic knowledge, the teaching of genetics at universities, and the publication of original and translated textbooks on genetics. Soon genetic laboratories were created in other cities of Russia. The achievements of Russian geneticists began to be increasingly used in practical work crop and livestock breeders.
1.3.2.3. The third stage of development of genetics (1920-1940)
The third stage in the history of genetics (1920-1940) was marked by the discovery of the possibility of artificially causing mutations. Charles Darwin knew about the existence of sudden hereditary changes - mutations. Mutations were intensively studied at the dawn of genetics by G. De Vries. Following him, geneticists paid great attention to the study of the mutations that arose. However, the causes of the mutations remained unknown. There was a fairly widespread opinion, going back to the views of Weisman and G. De Vries. According to these ideas, mutations arise spontaneously in the body, under the influence internal reasons, and do not depend on external influences. This concept was wrong. It gave rise to incorrect assumptions regarding driving forces evolution. It was later refuted by work on artificially inducing mutations.Rice. Hermann Möller (1890-1967).
The first evidence that mutations can be caused artificially was obtained in 1925 in Russia by G.A. Nadson and G.S. Filippov in experiments on irradiation of yeast with radium. Decisive evidence of the possibility of experimental induction of mutations was obtained in 1927 by G. Möller (Fig.) in experiments on the effect on Drosophila x-rays. The work of G. Möller caused a large number experimental research carried out on different species of plants and animals. The results of these works showed that ionizing radiation has a universal mutagenic effect. Then the mutagenic properties of ultraviolet rays were discovered and high temperature. Next came information that mutations were caused by certain chemicals. The first chemical mutagens were discovered in the 30s in Russia by the work of V.V. Sakharova, M.E. Lobashev and S.M. Gershenzon and his staff. A few years later, this direction acquired wide scope, especially thanks to the research of I.A. Rapoport in Russia and S. Auerbach in Great Britain.
Rice. Alexander Sergeevich Serebrovsky (1892-1948).
Research in the field of experimental mutagenesis has led to rapid progress in understanding the laws of the mutation process. They also contributed to the clarification of a number of questions concerning the fine structure of the gene. Of the Russian researchers, it should be noted A.S. Serebrovsky (fig.) who received data proving the complex structure of the gene. Detection of the mutagenic effect of radiation and chemical substances opened up new prospects for the practical use of genetic achievements. In different countries, work has begun on the use of radiation to create new forms of cultivated plants and animals. In Russia, the initiators of such “radiation selection” were geneticists A.A. Sapegin and L.N. Delaunay.
Rice. Sergei Sergeevich Chetverikov (1880–1959).
At the same third stage in the history of genetics, a direction arose with the goal of studying genetic processes in evolution. Fundamental work in this area was carried out by English geneticists R. Fisher and J. Haldane, American geneticist S. Wright and Russian geneticist S.S. Chetverikov (fig.). These scientists, relying on a large amount of factual material, convincingly showed that genetic data confirm and reinforce the basic principles of Darwinism. In the formation of evolutionary genetics, a major role was played by the work of S. S. Chetverikov and his colleagues, who carried out the first experimental studies of the genetic structure on several species of Drosophila natural populations. The study of comparative genetics and evolution of cultivated plants, headed by N. I. Vavilov, continued very successfully and on a large scale.
Rice. Georgy Dmitrievich Karpechenko (1899-1942).
Particularly noteworthy is the work of Vavilov’s collaborator, the talented geneticist Sergei Dmitrievich Karpechenko (1899-1942) (fig.), who experimentally reproduced one of the methods for the formation of new species in plants. S.D. Karpechenko achieved great success in creating distant hybrids and in 1935 published the monograph “The Theory of Distant Hybridization.” His work on distant hybridization of plants in a row similar works in terms of their importance they rank first. (S.D. Karpechenko was arrested by the NKVD in 1940 and died in prison in 1942).
In 1933 T. Paynter established genetic significance giant chromosomes from Drosophila salivary gland cells. In 1934, M. Schlesinger showed that the phage consists of DNA and proteins. In 1939, the work of E. Ellis and M. Delbrück began modern era research on phage genetics. They found that the phage penetrates the bacterium, multiplies in it and then lyses it.
The period from the twenties to the forties of the last century was a time of rapid development of genetics in Russia. These successes are associated with the activities of the largest Russian scientists and their schools: N.I. Vavilova, N.K. Koltsova, S.S. Chetverikova, A.S. Serebrovsky, Yu.A. Filipchenko, S.G. Navashina, I.V. Michurina, etc.
In the early twenties, N.I. Vavilov substantiated the law of homological series in hereditary variability. At that time, the idea that mutations were completely random was widely accepted. N.I. Vavilov, having discovered similar mutations in different species, established that the occurrence of mutations depends on the genetic properties of organisms. He showed that during selection, the necessary characteristics should be sought purposefully. N.I. Vavilov discovered world centers of plant origin, which contain sets of genes that are most valuable for breeding. Created under the leadership of N.I. Vavilov's world collection of cultivated plants and their wild ancestors became a source for the development of many hundreds of new varieties of a wide variety of crops. Around N.I. Vavilova rallied outstanding geneticists and cytologists. Talented student N.I. Vavilova G.D. Karpechenko (fig.) by doubling chromosomes for the first time overcame the sterility of hybrids obtained by crossing distant plant species. In 1927, he created a prolific intergeneric hybrid by crossing radish and cabbage. The method of doubling chromosomes in hybrids has become a classic method for selection and for experimentally reproducing the processes of origin of a number of species.
Sergei Gavrilovich Navashin (1857-1930) developed general doctrine about the structure of chromosomes and fertilization processes in plants. His student M.S. Navashin studied karyotypes of various species and structural mutations of chromosomes. G.A. Levitsky in 1931 substantiated the fragmentation theory of the appearance of structural mutations of chromosomes. His book " Material bases heredity" left a deep mark on the development of genetics in our country. He introduced the term “karyotype” into science.
Huge contribution to development Russian genetics contributed by the school of N.K. Koltsov. In 1927 N.K. Koltsov expressed the idea that when studying the phenomena of heredity one cannot limit oneself to the chromosomal level; the object of research should be the molecules from which the hereditary substance that is part of the gene is built. In keeping with his time, he believed that genes on chromosomes were represented by protein molecules. The main thing in the teachings of N.K. Koltsov had the idea of preserving the properties of genes based on their self-duplication: a daughter gene appears in the form of a molecular copy of the original gene. Such auto-reproduction can only be carried out by making copies from the original matrix thanks to physical and chemical processes. With regard to gene molecules, N.K. Koltsov formulated the principle “omnis molecule ex molecule” - each molecule from the molecule. This matrix principle of self-duplication was the ideological source of the subsequent development of molecular genetics.
The theoretical and experimental works of Sergei Sergeevich Chetverikov (1926, 1929) laid the foundation for modern population genetics.
A.S. Serebrovsky (1929) put forward the idea of genogeography and developed genetic methods for breeding domestic animals. IN Leningrad University the genetic school of Yu.A. Filipchenko, who successfully studied the variability of organisms. Yu.A. Filipchenko has the honor of writing the first textbook on genetics for higher education educational institutions. Works of I.V. Michurin enriched the theory and practice of selection. This outstanding breeder showed the importance of distant hybridization for developing new plant varieties.
Rice. Georgy Adamovich Nadson (1867-1940).
In 1925 G.A. Nadson (fig.) together with G.S. Filippov, in experiments with yeast, was the first to demonstrate the possibility of artificially obtaining mutations under the influence of ionizing radiation. In 1929–1930 A.A. Sapegin, L.N. Delaunay obtained radiomutants in wheat, demonstrating the significance of the new method for plant breeding.
In 1928, in the laboratory of G.A. Nadsona, M.N. Meisel using chloroform, coal tar and potassium cyanide induced mutations in yeast cells. After the work of M.E. Lobashev, V.V. Sakharov, S.M. Gershenzon, who appeared in the 30s, the possibility of chemical induction of mutations in the 50s was finally proven by the experiments of S. Auerbach and I.A. Rapoport.
Induced mutations turned out to be indispensable material for studying gene structure. In 1928–1932 N.P. Dubinin, A.S. Serebrovsky and other scientists who worked in the laboratory of A. S. Serebrovsky, in experiments with Drosophila, showed that the gene is split up: it consists of small structural units, arranged in linear order. It turned out that the mutations do not affect the gene as a whole, but only individual specified units. The discovery of the complex structure of the gene refuted the concept accepted at that time that the gene was elementary and indivisible.
During this period, domestic scientists S.G. Levit and S.N. Davidenkov organized extensive research on human genetics.
1.3.2.4. The fourth stage of development of genetics (1940-1953)
Most characteristic features This stage in the history of genetics was the development of work on the genetics of physiological and biochemical traits and the involvement in the circle of genetic experiments of completely new objects for genetics - microorganisms and viruses. This was of great importance, as it sharply increased the resolution of genetic analysis and made it possible to study many previously inaccessible aspects of genetic phenomena.
Studying biochemical processes, which underlie the formation of hereditary characteristics of different organisms (Drosophila, Neurospora mold, Escherichia coli bacteria, etc.) made it possible to establish how genes act.
Rice. George Wells Beadle (1903-1989).
In 1941, American geneticists (Fig.) and (Fig.) published a short article “Genetic control of biochemical reactions in Neurospora,” in which they reported the first genetic experiments on microorganisms. The article described biochemical mutations in Neurospora. The research results led J. Beadle and E. Tatem to an important generalization, according to which every gene determines the synthesis of one enzyme in the body. This formula: “one gene – one enzyme” was subsequently refined and began to sound: “one gene – one protein” or, more precisely, “one gene – one polypeptide”. Biochemical mutations have become the most important tool for analyzing the effect of genes on individual parts of biochemical syntheses. L. Pauling in 1949 showed that the cause of human disease - sickle cell anemia - is rooted in changes in the hemoglobin molecule. He called this phenomenon molecular diseases.
Rice. Edward Lawrie Tatum (1909-1975, Edward Lawrie Tatum)
Rice. Francis Crick
The discovery in 1944 was of great importance for the development of genetics. American geneticist O. Avery and collaborators on the nature of genetic transformation in bacteria. This work showed that the carrier of the hereditary potentials of the body is the deoxyribonucleic acid (DNA) of chromosomes. This conclusion was a powerful impetus to the study of the fine chemical structure, biosynthetic pathways and biological functions nucleic acids. Therefore, the work of O. Avery and his colleagues was the starting point for the development of molecular genetics and all molecular biology. Among the most important results achieved in this direction by the end of the period under consideration (fourth) is the establishment that the infectious element of viruses is their nucleic acid, the discovery in 1952 by American geneticists J. Lederberg and M. Zinder of the phenomenon of transduction (transfer by bacteriophages bacterial genes), and especially the elucidation of the structure of DNA in 1953 English physicist F. Crick (fig.) and American biologist James Watson.
Rice. James Watson
Great strides have been made in genetic and cytological studies of various hereditary human diseases. These advances were made possible largely due to the progress of biochemical genetics. They led to the formation and strengthening of a new direction, called medical genetics, which has as its main goal the prevention of hereditary human defects, including the prevention of the occurrence of harmful mutations from exposure to radiation and chemical mutagens.
Got further development work on the genetics of natural populations. They were carried out especially intensively in the USA by F. Dobzhansky and his collaborators and in Russia by N.P. Dubinin and his collaborators. During these same years, the first highly productive varieties of cultivated plants appeared, created on the basis of mutations artificially caused by radiation, attempts began to use chemical mutagens for this, and genetic methods of using heterosis were widely introduced into agricultural practice.
In Russia, at the beginning of the period under review, genetic research developed successfully and continued to occupy one of the leading places in the world. However, in Russia (USSR) back in the mid-30s, the views of T.D. began to be promoted, and from the mid-40s, the views of T.D. Lysenko, who completely denied Mendel's laws, the chromosomal theory of heredity, the doctrine of mutations, as well as a number of basic principles of Darwinism.
Russian geneticists of that time were creative people and they resisted Lysenkoism not only scientific articles with academic criticism of the vernalization of cereals, summer planting of potatoes and the transformation of birch into alder.
There was a parody of the tune of a popular song of those years:
Flowers bloomed on the branches
And the fogs floated over the river.
And the eggs matured in the flowers,
Pollinated by Presenta pollen
They were not pollinated by chance -
A secret marriage took place out of love,
And the pollen devoured the egg,
Like a cat and a mouse on an empty stomach
Oh, cell, pollen cell,
Curb your brutal appetite.
After all, your girlfriend is dear,
The egg also wants to live
You fly to Trofim's office.
And to the innovator - the giant of thought
Our formal say hello
Let him remember genes and gametes,
Chromosome reduction will understand.
Let him save the potatoes for the summer,
And Mendel will save science.
The most significant result of the August session of the All-Russian Academy of Agricultural Sciences was the almost complete destruction of the system of Academician I.I. Shmalhausen - the heaviest blow to Russian biology after the death of N.I. Vavilov, because this finally completed the destruction of the brilliant Russian school of Darwinists. Dark period national science certainly caused heavy damage to the world scientific community, because it deprived the leader of world biology, and the epicenter of scientific thought shifted to the west, to the homeland of the founder of Darwinism - Foggy Albion, where in 1953 the double helix was discovered - the structure of the DNA of the genetic material of a cell, which stores information about the hereditary characteristics of the organism. Russian Darwinism contained, so to speak, the most valuable gene pool of the science of genetics, and it was eliminated as a result of the “Jewish pogrom” in biology. Usually, when talking about the victims of this massacre, they do not mention the fact that, as a result, the leader of Russian geneticists, Professor S.S. Chetverikov, left science. After the August session, he wrote in a letter: “Now my life has swung to the other extreme: no lectures, no classes, no work at all... This was not entirely easy for me. On September 13th I had a heart attack (heart attack).” For 11 years, until his death, one of the most gifted geneticists on the planet remained in oblivion; in fact, scientific suicide has occurred. This is another of the most mournful traces of the dark period of Russian science [G. Gruzman, 2006].
The revival of genetics in Russia (USSR) began only in the early 60s, when biology began to free itself from the “ideologically consistent” views of supporters of T.D. Lysenko. The process of this liberation was very difficult. According to modern scientists and historians of science, the views of T.D. Lysenko were close to the medieval ones. (See supplementary material.)
However, Lysenkoism cannot be reduced only to a ban on genetics. Having reached its apogee in the middle of the current century (XX century. Note by V.I. Kryukov), and becoming truly a period of the Middle Ages in national biology and medicine, Lysenkoism also disfigured the methodology of these sciences, expelling from them, in particular, mathematics, and, first of all, statistics. The consequences of this deformity to this day do not allow biology and medicine to approach the status exact sciences[IN. Leonov].
However, even today there are defenders of the theoretical views of T.D. Lysenko. You can get acquainted with the apology of Lysenkoism from sources published on the Internet [Nazarenko N.; "Lysenko T.D. - reality and myth"; Mironin S.S., 2008; Mironin S.S., 2011].
1.3.2.5. The fifth, modern stage in the development of genetics (since 1953)
The fifth stage of genetics development continues from 1953 to the present.
The modern period of development of genetics began with the English physicist Francis Crick and the American biologist James Watson (Fig.). This work by F. Crick and J. Watson played outstanding role in all subsequent developments of molecular genetics and molecular biology.
Rice. James Watson and Francis Crick in 1953
For modern stage The history of genetics is most characterized by the study of genetic phenomena at the molecular level. This path was dictated by all previous developments of genetics. She penetrated deeper and deeper into the nature of genetic processes. The transition to work at the molecular level became possible thanks to the introduction of new chemical, physical and mathematical approaches and methods into genetics. The development of these methods, in turn, was associated with the progress of technology, the creation by industry of many advanced instruments and the production of complex reagents.
At this new stage in the development of genetics, outstanding discoveries, which played a big role in the progress of genetics and all biology. It was found that genes represent sections of giant polymer molecules of nucleic acids and differ in the number and order of the nucleotides they contain.
Rice. Erwin Chargaff.
The work of the American biochemist Erwin Chargaff (Fig.) showed that the structure of DNA is based on base pairing (A=T; C=G). English biophysicist Maurice Wilkins (Laureate Nobel Prize 1962) using X-ray diffraction analysis established the double-stranded structure of DNA molecules. This entire complex of biological and physicochemical knowledge led in 1953 to J. Watson and F. Crick to the construction of the double-stranded helical structure of the DNA molecule and its genetic interpretation. This work was a turning point for the development of biology in the 20th century. The genes turned out to be relatively small sets nucleotides in long polynucleotide chains, autoreproduction turned out to be a property double helix DNA molecules when each of the polynucleotide chains is converted into a template on which an identical (complementary) daughter DNA molecule is synthesized.
Rice. François Jacob (b. 1920) and Jacques Lucien Monod (1910-1976), Nobel Prize laureates in 1965.
Through the joint efforts of geneticists, physicists and biochemists, it was found that hereditary information is encoded in chemical structure genes. With only four bases included in all genes, it was obvious that their information should be realized only through the genetic code. In the late 50s - early 60s, F. Jacob, J. Mono, A. Lvov, F. Crick, S. Ochoa, M. Nirenberg and other researchers solved the problem of the genetic code and the transfer of genetic information from gene molecules to the cytoplasm where protein synthesis occurs.
Rice. Vermont M. Ingram (1924-2006).
In 1957 V.M. Ingram, professor of biology at the University of Massachusetts Institute of Technology, established that the molecular disease sickle cell anemia in humans occurs when there is a mutation in the hemoglobin gene by replacing just one nucleotide. In 1960, A. Levan and J. Thio accurately established the number of chromosomes in human cells. These two works started new stage molecular and cytogenetic studies of humans.
Rice. Gobind Khorana (1922–2011), Nobel laureate 1968
In 1969 in the USA, G. Horana and his colleagues synthesized chemically(outside the body) the first gene that is simple in structure. In the early 1970s, in several American laboratories, and then in laboratories in other countries, including Russia (USSR), several more complex genes of vertebrates were synthesized outside the body using special enzymes. Using model objects—bacteria and mammalian cell cultures—it was possible to introduce a certain gene into a cell and thereby change its hereditary properties in the desired direction.
Much has been done to understand the molecular mechanisms of mutations. Thanks to this, new powerful chemical mutagens (“super mutagens”) were discovered and studied. They were effectively used to obtain mutant forms of microorganisms, plants and animals. In the 70s, the doctrine of mutagens in the environment arose, surrounding a person, and formulated a fundamental problem about their possible threat to the heredity of humanity in the future. At the same time, work aimed at protecting the human genome from physical and chemical mutagenic environmental factors has made significant progress. Information about the molecular basis of the genetic regulation of the processes of individual development of organisms has deepened significantly.
A new revolution in genetics occurred in the mid-70s. It was associated with a new synthesis of knowledge obtained by geneticists from different fields: molecular and biochemical genetics, genetics of bacteriophages, bacteria and plasmids, genetics of yeast, mammals and Drosophila. Using knowledge about the organization of the hereditary apparatus of various model objects, geneticists developed technologies for manipulating genes, which were later called genetic engineering.
Rice. Barbara McClintock (), Nobel Prize laureate 1968
At the end of the 70s. ended Long story discovery of transposable genomic elements (MEGs) – obligatory non-permanently localized components of any genome. At the end of the 40s. Barbara McClintock discovered the system of mobile elements in corn and established the patterns of their movements. However, at that time, B. McClintock’s discovery did not find a wide response among geneticists. In 1976, the DNA of Drosophila transposable elements was isolated and cloned by the groups of G. P. Georgiev and V. A. Gvozdev in Russia and D. Hogness in the USA. In addition to theoretical knowledge about the existence of such a specific fraction of the genome, understanding the mechanisms of MEG movement turned out to be decisive in creating a transformation method in eukaryotes.
In the late 70s, geneticists developed a method for artificial cloning of large DNA fragments. This made it possible to reproduce “in vitro” the DNA fragments needed for research. In the mid-80s, another method of DNA cloning was proposed - the polymerase chain reaction (PCR) method. It allows you to synthesize the necessary DNA fragments and then repeatedly increase the number of their copies. This method makes it possible to obtain from small amounts of DNA (from one nucleus or even from one gene) the quantities necessary for biochemical analysis. The method is already very widely used, and not only in molecular biology, but also in history, ethnography and criminology. For example, using tiny amounts of DNA contained on sarcophagi and blankets of mummies or the bones of human ancestors, it was possible to generate volumes of DNA, after analysis of which interesting conclusions were drawn about the formation, evolution and migrations of ancestors modern people. Using PCR to analyze DNA from cells collected from evidence and comparing it with the DNA of victims and criminals, various crimes are solved. PCR DNA tests were decisive in identifying the remains of the latter's family Russian Emperor Nicholas II.
Using DNA sequencing methods, in the 90s. large groups of scientists are studying the genomes of more than 50 species. In 1992, a consortium of scientists (146 people from 35 European laboratories) reported sequencing the nucleotide sequences in the 3rd yeast chromosome Saccharomyces cerevisiae. In 1995, information was published about deciphering the genomes of the first bacteria - Haemophilus influenza And Mycoplasma genitalium. In 1997, the genome of the bacterium was sequenced Escherichia coli and already completely - the yeast genome S. cerevisiae. In February 1999, the genome of the nematode was sequenced Caenorhabditis elegans. In March 2000, a group of 200 scientists reported deciphering the Drosophila genome. In the spring of 2000, British scientists from Cambridge announced that they had basically sequenced the human genome. At the beginning of 2001, the human genome was deciphered almost completely large group scientists from the company “Celera” (USA).
After the phenomenon of transfer of genetic information (transformation) in prokaryotes was discovered (in 1944), attempts were constantly made to carry out such transfer in eukaryotes. In 1980, the first transgenic mice were produced by injecting cloned DNA into the pronucleus of a fertilized egg (J. Gordon et al.). In the same 1980, a technique was proposed for the effective transformation of cultured mammalian cells by microinjection of DNA directly into the nucleus.
Animal cloning experiments have become particularly famous. Back in the early 40s. G.V. Lopashov carried out the first transplantations of nuclei from some newt cells into nuclear-free fragments of the cytoplasm of eggs at the stage of 1-2 blastomeres. However, this work was not continued, first because of the war, and then because of the complete ban on genetics in Russia. In 1962, the English scientist J. Gurdon decided to find out whether the same set of genes that the zygote has is preserved in differentiated cells. To do this, he transplanted nuclei from a tadpole intestinal cell into a frog egg from which its own nucleus had been removed. As a result, a normal frog developed from such a hybrid egg. This indicated that the nuclei of somatic and germ cells are qualitatively identical. And if so, then as a result of each nuclear transplantation, a new animal can be obtained, and the transplantation of many nuclei, obtained from one animal, produces many animals, i.e., their clones. In 1997, a group of Scottish scientists led by A. Wilmut, using the nuclear transplantation technique, produced a sheep, the world famous Dolly. In 1999, scientists from the USA cloned a mouse and a cow, and in March 2000, five cloned piglets were born at once . According to the authors of this work, it will be possible to clone a person by 2005, but the first cloned children appeared already in January 2003.
Thus, in just one century (if we count from the rediscovery of Mendel’s laws in 1900), genetics has gone from forming ideas about discrete elements of heredity to creating new living organisms using genetic manipulation methods.
Boroday I.S. On the history of the formation and development of genetics as the theoretical basis of zootechnical science// Vestn. Tomsk state un-ta. -2012. -No. 359. -P.75-78.
Gershenfeld Anna (Ana Gerschenfeld). Nikolai Vavilov - the first custodian of plant biodiversity. Translation of an article published in the newspaper “Publico”, Portugal // Inosmi.ru, Russia today. . Date of publication: 04/03/2016
Zakharov I.A. Genetics in the twentieth century. History scores. -M.: Science. 2003. -92 p. Read online.
Lysenko T.D. and Lysenkoism is an ugly product of Bolshevism. Online materials.
Svanidze N. Lysenko and Vavilov. 1938 Historical chronicles . The history of the victory of Lysenkoism in the USSR. .
Main literature
Petukhov V.L. and etc. Veterinary genetics. Textbook for higher education agricultural, textbook. manager Specialty – 310800, veterinary medicine //Petukhov V.L., Zhigachev A.I., Nazarova G.A. – 2nd ed. – M.: Kolos, 1996. – 384 p.
Merkuryeva E.K. and etc. Genetics. Textbook for higher education agricultural textbook manager Specialty – 310700, animal science //Merkuryeva E.K., Abramova Z.V., Bakai A.V., Kochish I.I. – M.: Agropromizdat, 1991. – 446 p.
Lartseva S.Kh., Muxinov M.K. Workshop on genetics. – M.: Agropromizdat, 1985, – 288 p.
Additional and cited literature
Ayala F., Keiger J. Modern genetics. In 3 volumes. Trans. from English Volume 1. – M.: Mir, 1988. – 295 p.
Akimov O.E. War in biology. Lysenko - Vavilov. 2006-2015. Read online.
Alberts B. et al. Molecular biology cells. /Alberts B., Bray D., Lewis J. et al. In 5 volumes. Per. from English Volume 2. – M.: Mir, 1986. – 313 p.
Berkinblit M.B., Zherdev A.V., Larina S.N., Mushegin A.R., Chub V.V. Almost 200 problems on genetics.–M.: MIROS, 1992.–120 p.
Bogoyavlensky Yu.K., et al. Guide to laboratory classes in biology. /Bogoyavlensky Yu.K., Supryaga A.M., Ulissova T.N., Chebyshev N.V. –M.: Medicine, 1988. –320 p.
Brennan R. Dictionary of Scientific Literacy. –M.:Mir, 1997.–368 p.
Willi K., Dethier V. Biology (biological processes and laws). Per. from English –M.: Mir, 1974. –822 p.
Gaisinovich A.E. The origin and development of genetics. –M.: Science. 1988.– 424 p.
Gershenzon S.A. Fundamentals of modern genetics. Textbook for universities. –Kiev: Naukova Dumka, 1979. –508 p.
Glushchenko E.I. Vegetative hybridization of plants. –M.: OGIZ-SELKHOZGIZ. 1948. -240 p. Read online. Quote from the introduction to this opus: “Acad. T. D. Lysenko in his report “On the situation in biological science” showed the theoretical worthlessness and practical futility of Mendelism-Morganism. The theoretical basis of modern Weismannism - the so-called chromosome theory of heredity - is a purely speculative scholastic construction.
The Mendelists' assertion about the existence of an immortal substance of heredity is a myth, especially convincingly exposed in the experiments of the Michurinists on vegetative hybridization of plants.
Target of this work- to show the power of Michurin’s teaching about the mentor in application to annual crops, to reveal the patterns of inheritance of altered (during grafting) genetic characteristics...”
Golubovsky M.D. Confrontation.//Priroda.1990, No. 5. – P.86-92.
Green N. et al. Biology/Green N., Stout W., Taylor D. In 3 volumes. –M.: Mir, 1990.
Dubinin N.P. Genetics. Textbook for universities. – Chisinau: “Shtiintsa”, 1985. – 536 p.
Dubinin N.P. General genetics. –M.: Nauka, 1986. –572 p.
Dubinin N.P. Genetics - pages of history. – Chisinau: “Shtiintsa”, 1988. – 399 p.
Zhimulev I.F. General and molecular genetics. Textbook for universities. –Novosibirsk: NSU Publishing House, 2002. –459 p.
Zakharov I.K. A series of works on the history of genetics. See ICG SB RAS.
Zvyagina E. Protein heredity - new chapter genetics// “Science and Life”, 2001. No. 1. –P. 30-33.
Inge-Vechtomov S.G. Introduction to Molecular Genetics. Textbook for biol. specialist. Univ. –M.: graduate School, 1983, –343 p.
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Kryukov V.I. Genetics. Part 1. Introduction to genetics. Molecular basis heredity. – Orel: Publishing house Orel-GAU, 2006. – 192 p. from illus. The decision to assign the stamp UMO No. 06-523 dated May 26, 2006.
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1.1. Subject, purpose, problems and tasks of genetics
1.1.1. Subject, purpose, problems and tasks of genetics
1.1.1.1. Heredity
1.1.1.2. Variability
1.1.2. Problems and tasks of genetics
1.1.2.1. Theoretical problems of genetics
1.1.2.2. Practical problems of genetics
1.1.2.3. Objectives of veterinary genetics
1.2.1. Hybridological method
1.2.2. Genealogical method
1.2.3. Twin method.
1.2.4. Cytogenetic method
1.2.5. Somatic cell hybridization method.
1.2.6. Mutation method
1.2.7. Biochemical method
1.2.8. Molecular genetic method
1.2.9. Ontogenetic (phenogenetic) method
1.2.10. Population method.
1.2.11. Biometric method.
1.2.12. Mathematical modeling method
1.3.1. Prerequisites for the emergence of genetics
1.3.2. The main stages of development of genetics.
1.3.2.1. The first stage of development of genetics (1900-1910)
1.3.2.2. The second stage of development of genetics (1910-1920)
1.3.2.3. The third stage of development of genetics (1920-1940)
1.3.2.4. The fourth stage of development of genetics (1940-1953)
1.3.2.5. The fifth stage of development of genetics (since 1953)
1.4.1. The role of genetics in the development of medicine
1.4.2. The role of genetics in the development of biotechnology and genetic engineering
1.4.3. The role of genetics in the development of crop production.
1.4.4. The role of genetics in the development of livestock breeding.
1.4.4.1. Increasing role of selection and genetic prevention of animal diseases in the conditions of industrial technology
1.4.5. Prospects for the development of genetics and animal breeding.
Control questions.
Recommended reading
It's not genetics.
But you need to know.
- Soldering technology. This won't be shown on TV.
- For those who think. There is no need to watch if you are brainless.
- They sing well... Okay, if not for you.
Biology is the science of living organisms. As biology has developed, it has accumulated a lot of information. All this mass scientific information cannot be comprehended and analyzed by one researcher. Therefore, there was a need to differentiate this science. This is how botany (the science of plant organisms), zoology (the science of animal organisms), microbiology and other sciences. Genetics also emerged from biology.
Genetics is the science of heredity and variability of living organisms. Got its name from Greek word genesis (origin). The date of birth of genetics is considered to be 1900, when, independently of each other, three scientists G. De-Vries, K. Correns and E. Cermak rediscovered the laws established by G. Mendel in 1865. Currently, genetics occupies a central place in biology.
Heredity– the property of living organisms to ensure material and functional continuity between generations, as well as to determine the specific nature of the individual development of organisms. Each species of animals and plants retains its characteristic features in a series of generations: a chicken breeds chicks, a sheep gives birth to lambs, rye reproduces rye, etc., and each type of animal and plant, no matter where it is transported and no matter what conditions it is in placed, if it retains the ability to reproduce, it will reproduce its characteristics. Some species can remain relatively unchanged for millions of years. For example, the modern opossum is not much different from the opossum of the early Cretaceous period.
Along with the phenomenon of heredity, the subject of genetics research includes the study of variability. Variability- this is the difference between individuals of the same species, between ancestors and descendants, according to a number of characteristics and properties. If we carefully analyze a herd of black-and-white cows, then despite the general similarity of animals of this breed, we will find differences between them in weight, shape and location of spots, shape of horns, udder development, temperament and other characteristics. Among animals, no two organisms are completely similar friends on each other, with the exception of identical twins.
Like any science, genetics cannot develop independently, without connection with other sciences. It constantly borrows knowledge and achievements of other sciences. First of all, it is necessary to note the close connection between genetics and evolutionary teaching Ch. Darwin, integral part which she is. The main criteria of evolution are: change
generosity, heredity and natural selection. Genetics also studies these phenomena and helps to understand and explain scientific point view of many questions of evolution.
Cytology, the science of cell structure, had a significant influence on the development of genetics. Without deep knowledge It is impossible for cytology to understand material continuity between generations. It has been established that in a cell chromosomes are responsible for hereditary information. It is these organelles of the cell in to a greater extent interest geneticists.
Genetics is also related to biochemistry, since without knowledge chemical nature gene, it is impossible to imagine the processes of transmission of hereditary information and targeted intervention in these processes. General section genetics and biochemistry is a section of nucleic acids.
The use of viruses and bacteria as objects of research has led to a close connection between genetics and microbiology and virology. In particular, the development of genetic engineering is a successful combination of knowledge and achievements of these sciences.
Genetics widely uses in its research mathematical methods, primarily probability theory and variation statistics. First statistical method was successfully used to clarify the patterns of inheritance of traits by G. Mendel. Mathematical research methods are especially widely used nowadays to study the inheritance of economically useful traits in animals, which has led to the emergence of biometrics.
Theoretical knowledge, accumulated during the development of genetics, are found practical use. Breeders use this knowledge to create new varieties of plants and animal breeds. Thus, genetics is associated with selection, animal breeding and breeding.
Genetics methods. To understand the patterns of inheritance of traits and their variability, genetics uses a number of methods. The main method is hybridological. With this method, to identify patterns of inheritance of a particular trait, individuals that differ in this trait are crossed, and the resulting offspring are studied in the first and subsequent generations. The hybridological method was successfully used by G. Mendel for the first time in his research.
Genealogical The method is one of the hybridological options. Inheritance of a trait is studied by analyzing its transmission to offspring in entire families or related groups animals, for which pedigrees are compiled for several generations of ancestors, individuals and entire families. The genealogical method is of great importance in the study of the heredity of humans and slowly breeding animals, to which the usual hybridological method is either not applicable or requires a long time to obtain experimental results.
Cytological The method is used to study heredity at the cell and chromosome level. It has been established that many defects and violations
in the body are associated with changes in the number and structure of chromosomes. Therefore, when diagnosing some hereditary diseases in humans and animals, the cytological method is widely used.
Biochemical the method is used in genetics for a more in-depth analysis of metabolic disorders and their structure. This method is used for manipulation at the DNA level in genetic engineering.
Population-static The method is used when processing the results of crossings, studying the variability of traits and the relationship between them. When using this method, large numbers of plant or animal organisms are analyzed. This method is basic in biometrics.
Phenogenetic the method is used to establish the degree of influence of genes and environmental factors on the development of characteristics of an organism. When using this method, individuals with different heredities or those who are in different conditions environment.
In addition to the above methods, other methods are used in genetics: immunological, twin, ontogenetic.
History of the development of genetics. Russian geneticists. Thinkers and scientists have been thinking about the transmission of hereditary characteristics from parents to children since ancient times. But in those distant times, ideas about heredity and variability were very inaccurate and in many cases erroneous. This is how the ancient Greek scientist Empedocles explained the inheritance of traits in humans: “The formation of the embryo during pregnancy is subject to the imagination of women: they are often inflamed with love for statues or paintings and have children similar to these objects.”
Numerous studies on plant hybridization, carried out in the 18th and 19th centuries, gradually revealed certain patterns in the inheritance of traits. Famous Swedish scientist Karl Linnaeus, the creator of the system of flora and fauna, was involved in the hybridization of plants. Linnaeus put forward a theory about the inheritance of maternal and paternal characteristics, believing that in plants and animals internal parts and organs are inherited from the mother, external parts from the father.
In 1760-70, the botanist Koelreuter, as a result of experiments on tobacco hybridization, established that the hybrids had characteristics intermediate between the characteristics of both parents. This indicated the transmission of parental characteristics through both pollen and ovules. Koelreuter was the first to establish a phenomenon associated with the more powerful development of first-generation hybrids (the phenomenon of heterosis). However, Koelreuter and scientists working on plant hybridization after him failed to reveal the nature of the mechanism of heredity. This is explained by the fact that at that time they were not yet known cytological basics heredity.
Thomas Knight, Augustin Sarget, Charles Naudin and others made great contributions to the development of genetics.
Ch. Darwin was also interested in the problems of inheritance of characteristics. He formed his views on this problem in the “pangenesis hypothesis.” According to this hypothesis, special particles called gemmules are separated from each part of the body. These particles are carried by the blood to the germ cells. Subsequently, during the development of a new organism, from each particle the organ to which it belonged in the parent organism is formed. In this hypothesis, the fact of the transmission of characteristics through germ cells is correct, but at the same time, the assumption about the connection of body parts with germ cells through special particles - “gemmules” - is incorrect.
The famous German botanist Karl Naegeli proposed a speculative hypothesis of germplasm. Its main provisions are the existence of a special substance in the cell - idioplasm, which plays the role of a carrier of heredity, the recognition of the complete equivalence of all cells of the body in the phenomena of heredity and the assumption of the possibility of inheritance of acquired properties.
The significance of speculative hypotheses of heredity was primarily that they raised a number of questions that later became the subject of experimental research. These hypotheses introduced several new ideas into science, first of all, the assumption of the existence of special carriers of hereditary properties - genes that encode information about the characteristics of the organism.
For the first time, patterns of inheritance of traits in in full were discovered in 1865 by G. Mendel, who, based on experiments on crossing different varieties of peas, established the uniformity of hybrids of the first generation, the splitting of characters in a ratio of 3: 1 in the second generation and the independence of inheritance of various characters. These discoveries gave impetus to further work to check the described patterns on other types of plant and animal organisms. As a result, their universality was confirmed, and they acquired the status of laws.
In 1910, Thomas Morgan and his students, using the Drosophila fly as a research object and relying on the cytological data accumulated by that time, created a cytologically confirmed chromosomal theory of heredity. According to this theory, genes are localized on chromosomes in a strictly defined linear sequence for each of them and at a certain distance from each other.
Since the beginning of the 40s, intensive research into the phenomena of heredity and variability at the molecular level began. In 1944, the American scientist O. Avery and his colleagues showed that the leading role in the preservation and transmission of hereditary information belongs to DNA. This discovery marked the beginning of the development of molecular genetics.
J. Watson and F. Crick in 1953 deciphered the structure of the DNA molecule. After this it became clear how to encode hereditary information about the composition and structure of organisms. In the future, thanks to
scientific work Nirenberg and Ochoa, the genetic code was deciphered. In 1969, in the USA, Korana and his colleagues chemically synthesized a section of a DNA molecule or a simple gene outside the body. This and other works formed the basis of genetic engineering, which is rapidly developing at the present time.
Our domestic genetics has made a great contribution to the development of world science. Scientists in our country have discovered a number of the most important patterns heredity and variability.
Yu. A. Filipchenko is the founder of the first department of genetics in Russia St. Petersburg University. He has written more than a dozen books and brochures on genetics.
N.I. Vavilov carried out extensive experimental work. He organized and carried out more than 10 expeditions to inaccessible areas foreign countries on the study of centers of origin of cultivated plants. He wrote 8 books, created All-Union Institute plants (VIR) with a wide network of departments and experimental stations. N.I. Vavilov was the organizer and first director of the All-Russian Academy of Agricultural Sciences and the Institute of Genetics of the USSR Academy of Sciences. Starting with experimental work in the field of wheat genetics and plant immunity. N.I. Vavilov soon moved on to a broad study and generalization of the collected materials on all cultivated plants, which allowed him to discover the law of homologous series of hereditary variability. N.I. Vavilov was a talented organizer. He invited major geneticists from foreign countries to the institute he created. Thus, scientists from the USA worked at this institute - K. Bridges and G. Meller, the Bulgarian scientist D. Kostov and others.
N.K. Koltsov is the founder of experimental biology. He was a brilliant organizer of science, who rallied around himself a large number of students, many of whom later became prominent scientists (A. S. Serebrovsky, S. S. Chetverikov, B. L. Astaurov and others).
G. A. Nadson, together with G. S. Filippov, conducted research in 1925 to study the effect of X-rays on yeast fungi. Their work has proven the possibility experimental production mutants under the influence ionizing radiation. These works influenced the development and emergence of a new direction in genetics - radiation genetics.
G. D. Karpachenko is known for his work in the field of remote hybridization. Using the phenomenon of polyploidy, he was the first to succeed in obtaining interspecific hybrids of plants that cannot be crossed in the usual way. These theoretical developments are now successfully used by breeders in their work.
M. E. Lobashev, N. P. Dubinin, N. V. Tsitsin, V. V. Sakharov and others also made a great contribution to the development of domestic genetics.
The importance of genetics for practice . Genetics today occupies leading place in modern biology. The fundamental discoveries of this science are realized in plant selection and animal breeding. For the last
Over the years, hybrids of barley and wheat, barley and rye have been created, new varieties of wheat have been developed that can produce about 100 centners of grain per hectare, and high-oil sunflower varieties with a fat content in the seeds of up to 55%. Phytophthora-resistant and cancer-resistant potato varieties, polyploid varieties of sugar beets and fruit trees have been developed. The phenomenon of heterosis (more powerful development of first-generation hybrids compared to their parents) is widely used in animal husbandry. Almost all poultry farms in our country produce poultry meat using broilers, and hybrid poultry is used to produce eggs. This phenomenon is also used in pig farming and beef cattle breeding.
Today, immunogenetic methods are used to clarify the origin of animals when they are sold.
The developed methods of transplantation of fertilized eggs and embryos have found application in the reproduction of highly productive animals.
Genetic engineering methods are widely used in biotechnology (production industries needed by a person substances using living organisms). Using genetic engineering methods, industrial strains of microorganisms have been created that produce insulin (the hormone thyroid gland), interferon, somatotropin and other biologically active substances. Monoclonal antibodies obtained using hybridoma technology have found use in medicine and veterinary medicine.
Genetic methods are used in medicine for early diagnosis of certain hereditary diseases, protecting the human body from the negative effects of various factors and substances.
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Topic 1: Introduction to Genetics1. Genetics as the science of heredity and variability. Sections of genetics. The meaning of genetics. Genetics methods
2. Short story genetics. Features of the development of domestic genetics.
1. Genetics as the science of heredity and variability
Genetics is the science of heredity and variability of living organisms and methods of controlling them; is a science that studies heredity and variability of traits.
Heredity – the ability of organisms to give birth to their own kind; the ability of organisms to transmit their characteristics and qualities from generation to generation; the property of organisms to ensure material and functional continuity between generations.
Variability – the appearance of differences between organisms (parts of an organism or groups of organisms) according to individual characteristics; this is the existence of characteristics in various forms (variants).
The structure of modern genetics and its significance
All genetics (like any science) is divided into fundamental and applied.
Fundamental genetics studies general patterns inheritance of traits in laboratory or model species: prokaryotes (for example, E. coli), molds and yeasts, Drosophila, mice and some others. Fundamental genetics includes the following sections:
classical (formal) genetics,
cytogenetics,
molecular genetics,
genetics of mutagenesis (including radiation and chemical genetics),
evolutionary genetics,
population genetics,
genetics of individual development,
behavioral genetics,
environmental genetics,
mathematical genetics.
space genetics (studies the effect on the body cosmic factors: cosmic radiation, prolonged weightlessness, etc.).
Genetic (genetic) engineering is a branch of molecular genetics associated with the targeted creation in vitro of new combinations of genetic material capable of multiplying in a host cell and synthesizing end products of metabolism. It arose in 1972, when the first recombinant (hybrid) DNA (recDNA) was obtained in the laboratory of P. Berg (Stanford University, USA), in which DNA fragments of the lambda phage and Escherichia coli were combined with the circular DNA of the simian virus SV40.
In applied genetics, depending on the object of study, the following sections are distinguished: private genetics:
1. Genetics of plants: wild and cultivated: (wheat, rye, barley, corn; apple trees, pears, plums, apricots - about 150 species in total).
2. Genetics of animals: wild and domestic animals (cows, horses, pigs, sheep, chickens - about 20 species in total)
3. Genetics of microorganisms (viruses, prokaryotes, lower eukaryotes - dozens of species).
Human genetics is a special section of private genetics (there is special Institute medical genetics Academy of Medical Sciences of Russia)
Human genetics studies the characteristics of the inheritance of traits in humans, hereditary diseases (medical genetics), and the genetic structure of human populations. Human genetics is the theoretical basis modern medicine and modern healthcare (AIDS, Chernobyl). Several thousand actual genetic diseases are known, which are almost 100% dependent on the genotype of the individual. The most dangerous of them include: acid fibrosis of the pancreas, phenylketonuria, galactosemia, various shapes cretinism, hemoglobinopathies, as well as Down, Turner, and Klinefelter syndromes. In addition, there are diseases that depend on both the genotype and the environment: coronary disease, diabetes mellitus, rheumatoid diseases, peptic ulcers stomach and duodenum, many oncological diseases, schizophrenia and other mental diseases.
The tasks of medical genetics are to timely identify carriers of these diseases among parents, identify sick children and develop recommendations for their treatment. Big role In the prevention of genetically determined diseases, genetic-medical consultations and prenatal diagnostics (that is, detection of diseases on early stages development of the organism).
There are special sections of applied human genetics (environmental genetics, pharmacogenetics, genetic toxicology) that study the genetic basis of healthcare. During development medicines, when studying the body's response to exposure unfavorable factors need to consider how individual characteristics people and the characteristics of human populations.
Genetics methods
The set of methods for studying the hereditary properties of an organism (its genotype) is called genetic analysis.Depending on the task and characteristics of the object being studied, genetic analysis is carried out on population, organism, cellular and molecular levels.
The basis of genetic analysis is hybridological analysis , based on the analysis of the inheritance of traits during crossings. Hybridological analysis, the foundations of which were developed by the founder of modern genetics G. Mendel, is based on the following principles.
1. Use as initial individuals (parents) of forms that do not produce splitting during crossing, i.e. constant forms .
2. Inheritance analysis individual pairs of alternative characteristics , that is, features represented by two mutually exclusive options.
3. Quantitative accounting forms released during successive crossings and the use of mathematical methods in processing the results.
4. Individual analysis offspring from each parent.
5. Based on the results of crossing, a crossbreeding scheme.
Hybridological analysis is usually preceded by selection method . With its help, the selection or creation of source material is carried out, subject to further analysis (for example, G. Mendel, who is essentially the founder of genetic analysis, began his work by obtaining constant - homozygous - forms of peas through self-pollination);
However, in some cases, the method of direct hybridological analysis is not applicable. For example, when studying the inheritance of traits in humans, it is necessary to take into account a number of circumstances: the impossibility of planning crosses, low fertility, a long period puberty. Therefore, in addition to hybridological analysis, many other methods are used in genetics.
Cytogenetic method . It consists of a cytological analysis of genetic structures and phenomena based on hybridological analysis in order to compare genetic phenomena with the structure and behavior of chromosomes and their sections (analysis of chromosomal and genomic mutations, construction of cytological maps of chromosomes, cytochemical study of gene activity, etc.). Special cases of the cytogenetic method - karyological, karyotypic, genomic analysis .
Population method . Based on the population method, the genetic structure of populations of various organisms is studied: the distribution of individuals of different genotypes in the population is quantitatively assessed, the dynamics of the genetic structure of populations is analyzed under the influence of various factors (the creation of model populations is used).
Molecular genetic method is a biochemical and physicochemical study of the structure and function of genetic material and is aimed at elucidating the stages of the “gene? sign" and the mechanisms of interaction of various molecules along this path.
Mutation method allows (based on a comprehensive analysis of mutations) to establish the features, patterns and mechanisms of mutagenesis, helps in the study of the structure and function of genes. The mutation method acquires particular importance when working with organisms that reproduce asexually and in human genetics, where the possibilities of hybridological analysis are extremely difficult.
Genealogical method (method of pedigree analysis). Allows you to trace the inheritance of traits in families. It is used to determine the hereditary or non-hereditary nature of a trait, dominance or recessiveness, chromosome mapping, i.e. to establish whether the gene encoding a given trait belongs to certain group adhesion, adhesion with X- or Y-chromosomes, to study the mutation process, especially in cases where it is necessary to distinguish newly emerged mutations from those that are familial in nature, i.e., arose in previous generations. Usually, genealogical method forms the basis for conclusions in medical genetic counseling (if we are not talking about chromosomal diseases).
Twin method , which consists in analyzing and comparing the variability of characteristics within various groups twins, allows us to assess the relative role of the genotype and external conditions in the observed variability. This method is especially important when working with low-fertility organisms that have late stages of puberty (for example, cattle), as well as in human genetics.
Many other methods are also used in genetic analysis:
ontogenetic ,
immunogenetic,
comparative morphological And comparative biochemical methods,
biotechnology methods,
various mathematical methods etc.
2. Brief history of genetics
The phenomena of heredity and variability of traits have been known since ancient times. The essence of these phenomena was formulated in the form of empirical rules: “The apple doesn’t fall far from the tree”, “Do not expect a good breed from a bad seed”, “Not into a mother, not into a father, but into a passing young man”, etc.
Natural philosophers ancient world tried to explain the reasons for the similarities and differences between parents and their descendants, between brothers and sisters, the mechanisms of sex determination, and the reasons for the birth of twins. The continuity of generations was described by the terms “genus” (genus), “gennao” (giving birth), “geneticos” (related to origin), “genesis” (origin).
In modern times in England (T. Knight), Germany (J. Kölreuter), France (O. Sajray), methods for conducting experiments on hybridological analysis were developed, the phenomena of dominance and recessivity were discovered, and ideas about elementary inherited traits were formulated. However, to reveal the mechanisms of heredity and variability for a long time it didn't work out. To explain the phenomena of heredity and variability, the concepts of inheritance of acquired traits, panspermia, variability of traits under the direct influence of the environment, etc. were used.
Modern genetics is based on the patterns of heredity discovered by G. Mendel when crossing different varieties of peas (1865), as well as the mutation theory of H. De Vries (1901–1903). However, the birth of genetics is usually attributed to 1900, when H. De Vries, K. Correns and E. Cermak rediscovered G. Mendel’s laws.
In 1906, based on the root “gene”, W. Bateson (England) proposed the term “genetics”, and in 1909 V.L. Johannsen proposed the term "gene".
Back in 1883–1884. V. Roux, O. Hertwig, E. Strassburger, and A. Weissman (1885) formulated the nuclear hypothesis of heredity, which at the beginning of the 20th century. developed into the chromosomal theory of heredity (W. Setton, 1902–1903; T. Boveri, 1902–1907; T. Morgan and his school).
T. Morgan also laid the foundations of the gene theory, which was developed in the works of domestic scientists of the school of A.S. Serebrovsky, who formulated it in 1929–1931. ideas about the complex structure of the gene. These ideas were developed and concretized in studies of biochemical and molecular genetics, which led to the creation of a DNA model by J. Watson and F. Crick (1953), and then to the deciphering of the genetic code that determines protein synthesis.
A significant role in the development of genetics was played by the discovery of mutagenesis factors - ionizing radiation (G. A. Nadson and G. S. Filippov, 1925; G. Möller, 1927) and chemical mutagens (V. V. Sakharov and M. E. Lobashev, 1933 –1934). The use of induced mutagenesis contributed to an increase in the resolution of genetic analysis and provided breeders with a method for expanding inheritance and variability of the starting material.
The works of N.I. were important for the development of the genetic basis of selection. Vavilova. The law of homological series in hereditary variability, formulated by him in 1920, allowed him to subsequently establish the centers of origin of cultivated plants, in which the greatest diversity of hereditary forms is concentrated.
The works of S. Wright, J. B. S. Haldane and R. Fisher (20-30s) laid the foundations for genetic and mathematical methods for studying processes occurring in populations. A fundamental contribution to population genetics was made by S. S. Chetverikov (1926), who united the laws of Mendelism and Darwinism in a single concept.
Features of the development of domestic genetics
The development of genetics in our country began in the early years Soviet power. In 1919, the Department of Genetics was created at Petrograd University, headed by Yuri Aleksandrovich Filipchenko. In 1930, the Laboratory of Genetics of the USSR Academy of Sciences was opened under the leadership of Nikolai Ivanovich Vavilov (since 1933 - Institute of Genetics).
In the 1920s–1930s. our country was a leader in all areas of genetics
Koltsov Nikolai Konstantinovich - predicted the properties of carriers of genetic information; developed the gene theory; developed the doctrine of social genetics (eugenics).
Vavilov Nikolai Ivanovich - formulated the law of homological series, developed the doctrine of a species as a system.
Michurin Ivan Vladimirovich - discovered the possibility of controlling dominance.
Serebrovsky Alexander Sergeevich - created the doctrine of the gene pool and genogeography: “I called the totality of all the genes of a given species the gene pool in order to emphasize the idea that in the form of the gene pool we have the same national wealth as in the form of our coal reserves hidden in our depths "
Chetverikov Sergei Sergeevich - in his work “On some aspects of the evolutionary process from the point of view of modern genetics” he proved the genetic heterogeneity of natural populations.
Dubinin Nikolai Petrovich - proved the divisibility of the gene; independently of Western researchers, he established that probabilistic, genetic-automatic processes play an important role in evolution.
Shmalhausen Ivan Ivanovich - developed the theory of stabilizing selection; discovered the principle of integration of biological systems.
Nikolai Vladimirovich Timofeev-Resovsky - laid the foundations of modern population genetics.
At the August (1948) session of VASKhNIL, power in science was seized by the president of VASKhNIL, academician T.D. Lysenko. He contrasted scientific genetics with a false teaching called “Michurin biology.” Many genetic scientists (N.P. Dubinin, I.A. Rapoport) were deprived of the opportunity to engage in science. Only in 1957 M.E. Lobashev resumed teaching genetics. In 1965 T.D. Lysenko, under pressure from the progressive public (mathematicians, chemists, physicists), lost his monopoly on scientific truth. The Institute of General Genetics of the USSR Academy of Sciences was created, the Society of Genetics and Breeders named after. N. I. Vavilova. At the end of the 1960s. our country has regained its lost position in world science.
GENETICS, a science that studies heredity and variability - properties inherent in all living organisms. The endless variety of species of plants, animals and microorganisms is supported by the fact that each species retains its characteristic features over generations: in the cold North and in hot countries, a cow always gives birth to a calf, a hen breeds chicks, and wheat reproduces wheat. At the same time, living beings are individual: all people are different, all cats are somehow different from each other, and even ears of wheat, if you look at them more closely, have their own characteristics. These two the most important properties living beings - to be similar to their parents and different from them - and constitute the essence of the concepts of “heredity” and “variability”.
Origins of genetics
The origins of genetics, like any other science, should be sought in practice. Since people started breeding animals and plants, they began to understand that the characteristics of offspring depend on the properties of their parents. By selecting and crossing the best individuals, man from generation to generation created animal breeds and plant varieties with improved properties. The rapid development of breeding and plant growing in the second half of the 19th century. gave birth to increased interest to the analysis of the phenomenon of heredity. At that time, it was believed that the material substrate of heredity is a homogeneous substance, and the hereditary substances of parental forms are mixed in the offspring in the same way as mutually soluble liquids are mixed with each other. It was also believed that in animals and humans, the substance of heredity is somehow connected with blood: the expressions “half-breed”, “purebred”, etc. have survived to this day.
It is not surprising that contemporaries did not pay attention to the results of the work of the abbot of the monastery in Brno, Gregor Mendel, on crossing peas. None of those who listened to Mendel’s report at a meeting of the Society of Naturalists and Physicians in 1865 were able to unravel the fundamental biological laws in some “strange” quantitative relationships discovered by Mendel when analyzing pea hybrids, and in the person who discovered them, the founder new science- genetics. After 35 years of oblivion, Mendel's work was appreciated: his laws were rediscovered in 1900, and his name entered the history of science.
Laws of genetics
The laws of genetics, discovered by Mendel, Morgan and a galaxy of their followers, describe the transmission of traits from parents to children. They argue that all heritable traits are determined by genes. Each gene can be present in one or more forms called alleles. All cells of the body, except sex cells, contain two alleles of each gene, i.e. are diploid. If two alleles are identical, the organism is said to be homozygous for that gene. If the alleles are different, the organism is called heterozygous. Cells involved in sexual reproduction (gametes) contain only one allele of each gene, i.e. they are haploid. Half of the gametes produced by an individual carry one allele, and half carry the other. The union of two haploid gametes during fertilization results in the formation of a diploid zygote, which develops into an adult organism.
Genes are specific pieces of DNA; they are organized into chromosomes located in the cell nucleus. Every species of plant or animal has certain number chromosomes. In diploid organisms, the number of chromosomes is paired; two chromosomes of each pair are called homologous. Let's say a person has 23 pairs of chromosomes, with one homolog of each chromosome obtained from the mother and the other from the father. There are also extranuclear genes (in mitochondria, and in plants, also in chloroplasts).
Features of the transmission of hereditary information are determined by intracellular processes: mitosis and meiosis. Mitosis is the process of distributing chromosomes to daughter cells during cell division. As a result of mitosis, each chromosome of the parent cell is duplicated and identical copies disperse to the daughter cells; in this case, hereditary information is completely transmitted from one cell to two daughter cells. This is how cell division occurs in ontogenesis, i.e. process of individual development. Meiosis is a specific form of cell division that occurs only during the formation of sex cells, or gametes (sperm and eggs). Unlike mitosis, the number of chromosomes during meiosis is halved; each daughter cell receives only one of the two homologous chromosomes of each pair, so that in half of the daughter cells there is one homologue, in the other half there is another; in this case, chromosomes are distributed in gametes independently of each other. (The genes of mitochondria and chloroplasts do not follow the law of equal distribution during division.) When two haploid gametes merge (fertilization), the number of chromosomes is restored again - a diploid zygote is formed, which received a single set of chromosomes from each of the parents.
Methodological approaches.
Thanks to what features of Mendel's methodological approach was he able to make his discoveries? For his crossing experiments, he chose pea lines that differed in one alternative trait (seeds are smooth or wrinkled, cotyledons are yellow or green, the shape of the bean is convex or constricted, etc.). He analyzed the offspring from each cross quantitatively, i.e. counted the number of plants with these characteristics, which no one had done before. Thanks to this approach (the selection of qualitatively different characteristics), which formed the basis for all subsequent genetic research, Mendel showed that the characteristics of parents are not mixed in offspring, but are passed on unchanged from generation to generation.
Mendel's merit also lies in the fact that he gave geneticists powerful method research of hereditary characteristics - hybridological analysis, i.e. a method of studying genes by analyzing the characteristics of the descendants of certain crosses. Mendel's laws and hybridological analysis are based on events occurring in meiosis: alternative alleles are found on homologous chromosomes of hybrids and therefore diverge equally. It is the hybridological analysis that determines the requirements for objects of general genetic research: these must be easily cultivated organisms that produce numerous offspring and have a short reproductive period. Among higher organisms, these requirements are met by the fruit fly Drosophila - Drosophila melanogaster. For many years it became a favorite object of genetic research. Through the efforts of geneticists from different countries, fundamental genetic phenomena. It was found that genes are located linearly on chromosomes and their distribution in descendants depends on the processes of meiosis; that genes located on the same chromosome are inherited together (gene linkage) and are subject to recombination (crossing over). Genes localized in sex chromosomes have been discovered, the nature of their inheritance has been established, and the genetic basis of sex determination has been identified. It has also been discovered that genes are not immutable, but are subject to mutation; that the gene is complex structure and there are many forms (alleles) of the same gene.
Then microorganisms became the object of more scrupulous genetic research, in which the molecular mechanisms of heredity began to be studied. Yes, on coli Escherichia coli The phenomenon of bacterial transformation was discovered - the inclusion of DNA belonging to a donor cell into a recipient cell - and for the first time it was proven that DNA is the carrier of genes. The structure of DNA was discovered, the genetic code was deciphered, the molecular mechanisms of mutations, recombination, genomic rearrangements were revealed, the regulation of gene activity, the phenomenon of movement of genome elements, etc. were studied. cm. CELL; HEREDITY; MOLECULAR BIOLOGY) . Along with these model organisms, genetic studies were carried out on many other species, and the universality of the basic genetic mechanisms and methods for studying them was shown for all organisms - from viruses to humans.