Y-chromosome

In the body of every man there is a so-called Y-chromosome that makes a man a man. Typically, chromosomes in the nucleus of any cell are arranged in pairs. For Y- paired chromosome is X-chromosome. At conception, the future new organism inherits all of its genetic information from parents (half the chromosomes from one parent, half from the other). From his mother he can only inherit X- chromosome, from the father - either X, or Y. If an egg contains two X- chromosomes, a girl will be born, and if X- And Y- chromosomes - boy.

For almost 100 years, geneticists believed that the tiny chromosome (a Y-the chromosome is really the smallest, noticeably smaller X-chromosome) is simply a “stub”. The first guesses that the chromosome set of men differs from that of women were put forward in the 1920s. Y-chromosome was the first chromosome discovered using a microscope. But to determine the presence of any genes localized in Y- chromosome turned out to be impossible.

In the middle of the 20th century. geneticists have suggested that several very specific genes may be contained in Y- chromosome. However, in 1957, at a meeting of the American Society of Human Genetics, these hypotheses were criticized. Y- the chromosome was officially recognized as a “dummy”, not carrying any important hereditary information. The point of view has been established that “ Y“The chromosome, of course, carries some kind of gene that determines the sex of a person, but no other functions are assigned to it.”

Just 15 years ago Y- chromosome did not cause scientists special interest. Now decryption Y- chromosomes is part of a project to decipher the human genome, which is carried out by an international group of geneticists. During the study it became clear that Y-the chromosome is far from being as simple as it seemed at first. Information about genetic map this chromosome is extremely important, because It is here that the answers to questions about the causes of male infertility lie.

Research Y- chromosomes may provide answers to many other questions: Where did man appear? How did the language develop? What makes us different from monkeys? Is the “war of the sexes” really programmed into our genes?

Now geneticists have begun to understand that Y-chromosome is something unique in the world of chromosomes. It is extremely highly specialized: all the genes contained in it (and there were about two dozen of them) are responsible either for the production of sperm by the male body, or for “related” processes. And, naturally, the most important gene on this chromosome is SRY– in the presence of which the human embryo develops along the male path.

Approximately 300 million years ago, it did not exist in nature Y- chromosomes. Most animals had a pair X- chromosomes, and sex was determined by other factors such as temperature (in some reptiles such as crocodiles and turtles, the same egg can still hatch into either a male or female, depending on temperature). Then a mutation occurred in the body of a certain mammal, and the new gene that appeared began to determine the “male type of development” for carriers of this gene.

Gene survived in natural selection, but for this he needed to block the replacement process allelic gene from X-chromosomes. These long-standing events determined the uniqueness Y- chromosomes: it is found only in male organisms. Investigating mutations in Y- chromosome, scientists can estimate how distant (in a genetic sense) men from two ethnic groups are from our common ancestor. Some of the results obtained in this way were quite surprising.

Last November, a branch of biology called archaeogenetics took a big step forward. Leading scientific journal, Nature Genetics, offered new version family tree humanity, based on hitherto unknown variations, so-called haplotypes Y- chromosomes. These data confirmed that the ancestors modern people migrated from Africa.

It turned out that “genetic Eve,” the progenitor of all humanity, is 84 thousand years older than “genetic Adam,” if age is measured by Y- chromosome. Female equivalent Y- chromosomes, i.e. The genetic information passed only from mother to daughter is known as m-DNA. This is the DNA of mitochondria, which is the source of energy in the cell.
For the past few years, it has been generally accepted that "mitochondrial Eve" lived about 143 thousand years ago, which does not fit with the estimated age of "Adam" of 59 thousand years.

In fact, there is no contradiction here. These data only suggest that the different chromosomes found in human genome, appeared in different time. About 143 thousand years ago, a new variety of m-DNA appeared in the gene pool of our ancestors. It, like any successful mutation, spread more and more widely until it crowded out all other varieties from the gene pool. This is why all women now carry this new, improved version of m-DNA. The same happened with Y- chromosome in men, but it took evolution another 84 thousand years to create a version that could displace all competitors.

It is not yet clear what the success of these new versions was based on: perhaps an increase in the reproductive ability of the offspring of their carriers.

Research Y-chromosomes not only allow us to trace migrations ancient peoples, but they can also tell what part of the genome a man shares with another bearer of the same surname (since both the man’s surname and his Y-chromosomes are inherited through the male line). This technique can also be used to determine the alleged name of the criminal based on traces of his DNA at the crime scene.

Data obtained during the study Y-chromosomes confirm that the “war of the sexes” is programmed in genes. What men and women have are different life programs, is now common knowledge. While a man can theoretically have an almost unlimited number of natural children, women are limited in this.

Special position Y- chromosome allows the genes located on it to influence only the male individual and “not worry” about how they affect female individuals.

It was found that the genes responsible for the production of sperm proteins mutate very quickly, apparently due to intense competition. Y-chromosome contains a large number of these genes, and researchers are now trying to understand which ones are involved in this competition.

Availability Y- chromosome is a risk factor for the fetus due to the maternal immune response. This may explain some interesting patterns. For example, according to statistics, the more older brothers a man has (namely, brothers, not sisters), the more likely he is to develop homosexual tendencies. One possible explanation for this fact is that in Y- There is a gene on the chromosome responsible for the production of a masculinizing hormone called AMH. This hormone stops the development of glands, which, in its absence, turn into the uterus and ovaries. In addition, AMN causes an immune reaction on the part of the mother’s body, and the antibodies produced in this process prevent the hormone from performing another important function, namely, directing the development of the fetal brain according to male type.

Isolation is one of the most important features Y- chromosomes. Copying genes is accompanied by errors. When eggs and sperm are formed, parts of the paired chromosomes are swapped, and the damaged areas are discarded. But Y-the chromosome has closed its borders, and this creates “abandoned lands” where repair and renewal of genes does not occur. Therefore, gene structures gradually decline, and once functional genes become useless.

The common picture of DNA copying as something like photocopying fails to convey the true dynamism of the genome. Although nature has tried to ensure the maximum accuracy of this procedure, just one piece of DNA, like an asteroid invading someone else's chromosome, can instantly change the sequence carefully preserved for many thousands of generations. These uninvited guests are called jumping genes, or transposons.

The vast majority of genes never leave their original chromosome. In contrast, jumping genes are “genome wanderers.” Sometimes they “jump” from one chromosome and “land” in a random place on another. They can insert themselves into the middle of a gene, causing chaos, or they can “moor” at the edge, slightly modifying its function. Aliens are usually “expelled” from ordinary chromosomes due to endless mixing of genes, but once on Y-chromosome they remain in it for millions of years. Sometimes, quite by accident, it allows them to do something wonderful. "Jumping emigrants" could turn Y-chromosome into the start button that starts evolution. The first of these Y- there were immigrants DAZ, discovered by D. Page (USA).

At the time when D. Page began to study Y-chromosome, all that was known about it was that it contained a gene SRY, which in right moment triggers the development of male organs in the embryo. It is now known that Y-chromosome contains more than twenty genes (compare with 2 thousand genes in X-chromosome). Most of these genes are involved in sperm production or help the cell synthesize proteins. Gene DAZ probably arrived in Y- chromosome about 20 or 40 million years ago, approximately when the first primates appeared (perhaps the reason for their appearance was DAZ). The absence of this gene in a man’s body leads to a decrease or complete absence spermatogenesis. According to statistics, one in six couples have problems conceiving a child, and for 20% of them key factor- namely male sperm.

Currently, ectopic fertilization technology partially solves this problem. But bypassing the laws of nature is not in vain. Infertility, as paradoxical as it may sound, becomes hereditary.

Recently, British researchers made a bold assumption: the critical factor in the emergence of speech in humans was precisely a certain “jumping gene” that invaded Y-chromosome.

Gene DAZ by enhancing spermatogenesis allowed primates to flourish, but what gene was the impetus for the separation of humans from the primate lineage? A direct way to find it is with the human and chimpanzee genomes. A more elegant way is to imagine what the consequences of such mutations would be and where these mutations might be found.

This is exactly what was done at Oxford. At first, researchers assumed that there was a certain gene that had such an influence on brain development what has become possible speech. Moreover, it was suggested that this gene takes a different form in men and women.

At a conference in London in 1999, another research group announced that in Y-gene detected on chromosome PCDH, whose activity most likely affects the functioning of the human brain, but not primates. This makes it good candidate for the role of the speech gene. Primates have it X-version ( PCDHX), but at some point in evolution it jumped to Y- chromosome.

Scientists have been able to trace the connection Y-versions of this gene ( PCDHY) with two turning points in human evolution. The first of these occurred about 3 million years ago, when the size of the human brain increased and the first tools appeared. But that is not all. A piece of DNA carrying PCDHY, transformed again, splitting into two parts, so that the resulting segments turned over in their places. According to scientists, this happened 120–200 thousand years ago, i.e. just at the time when great changes took place in the manufacture of tools.

Human African ancestors developed the ability to transmit information using symbols. Circumstantial evidence is all well and good, but how does this gene actually function? On this moment there are more questions than answers here, but the available data do not contradict the theory about the connection of this gene with the appearance of speech. It is likely one of a family of genes known as cadhedrins. They synthesize proteins that make up the membrane of nerve cells and are thus involved in the transmission of information. Genes PCDHX/Y active in some areas of the human fetal brain.

But behind all these discoveries lies one big mystery. Y- the chromosome can be thought of as a model of a capitalist economy. The winners, the genes that give an advantage, take everything because they don't mix with genes from other chromosomes. Outsiders, because they usually affect fertility, going bankrupt almost instantly. That is, the genes that survive here must do something truly valuable for the organism.

More likely, Y-chromosome has lost most of its genes during evolution, but all the remaining genes thrive. They must perform some elusive function, incomprehensible to us. Probably, to clarify this function, it is necessary to investigate the connection genetic markers, allowing you to trace a person’s ancestry with his abilities. The idea is dangerous in terms of ethical correctness, but it will provide an opportunity Y- chromosome will surprise us more than once.

How does the process of birth of men and women take place? The X and Y chromosomes are responsible for this. And it all begins when 400 million sperm rush to search for an egg. It's not that much difficult task, as it might seem at first glance. IN human body The egg can be compared to a huge star, towards which small sperm star fighters are rushing from all sides.

Now let's talk about chromosomes. They contain all the information necessary for the creation of man. A total of 46 chromosomes are needed. They can be compared to 46 thick volumes of an encyclopedia. Each person receives 23 chromosomes from their mother, and the remaining 23 from their father. But only 2 are responsible for sex, and one must be the X chromosome.

If you get a set of 2 X chromosomes, you will use the women's restroom for the rest of your life. But if the set consists of X and Y, then in this case you are doomed to go to the men's room for the rest of your days. At the same time, you need to know that the man bears full responsibility for gender, since the Y chromosome is contained only in the sperm, and it is absent in the egg. So the birth of boys or girls is entirely dependent on male genetic material.

A remarkable fact is that to recreate the male sex, the Y chromosome is not needed at all. Only an initial push is needed to start the development program of the male body. And it is provided by a special sex determination gene.

X and Y chromosomes are not equal. The first one takes on the main work. And the second only protects the genes associated with it. There are only 100 of them, while the X chromosome carries 1,500 genes.

From each X chromosome, one gene is needed to form the male sex. And for the formation of the female sex, two genes are needed. It's like a pie recipe with one cup of flour. If you take two glasses, then everything will change dramatically.

However, you should know that the female embryo, having two X chromosomes, ignores one of them. This behavior is called inactivation. This is done so that 2 copies of the X chromosomes do not produce twice as many genes as required. This phenomenon referred to as gene dosage compensation. An inactivated X chromosome will be inactive in all subsequent cells resulting from division.

This shows that the cells of a female embryo form a rather complex mosaic, assembled from inactive and active paternal and maternal X chromosomes. As for the male embryo, no inactivation of the X chromosome occurs in it. This means that women are genetically more complex than men. This is a rather loud and bold statement, but a fact is a fact.

But as for the genes of the X chromosome, of which there are 1,500, many of them are associated with brain activity and determine human thinking. We all know that the chromosome sequence of the human genome was determined in 2005. It was also found that high percent X chromosome genes ensure the generation of a protein that is involved in the formation of the medulla.

Some of the genes are involved in the formation of the brain mental activity. These are verbal skills social behavior, intellectual abilities. Therefore, today scientists consider the X chromosome to be one of the main points of knowledge.

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Subtitles

Genes, DNA and chromosomes are what make us unique. They are a set of instructions passed down to you from your father and mother. These instructions are found in your cells. And all living organisms are made up of cells. There are many types of cells - nerve cells, hair cells or skin cells. They all differ in shape and size, but each has certain components. The cell has an outer boundary called the membrane, which contains a fluid called the cytoplasm. The cytoplasm contains the nucleus, in which the chromosomes are located. Each human cell usually has 23 pairs of chromosomes, or 46 in total. 22 pairs of these are called autosomes and are the same in men and women. The 23rd pair are sex chromosomes; they are different in men and women. Women have 2 X chromosomes, men have one X and one Y chromosome. Chromosomes are long molecules of DNA - deoxyribonucleic acid. The shape of DNA resembles a twisted ladder. And it's called a double helix. The steps in the ladder are 4 bases: Adenine - A Thymine - T Guanine - G And Cytosine - C A section of DNA is called a gene. The body reads genes as recipes for making proteins. The length and order of bases in the DNA of genes determines the size and shape of the resulting proteins. The size and shape of a protein determine its function in the body. Proteins make up the cells that form the tissues that make up organs, such as our eyes or skin. Thus, genes determine whether you are a cow, an apple or a person and what you look like - the color of your hair, skin, eyes and everything else.

General information

The cells of most mammals contain two sex chromosomes: a Y chromosome and an X chromosome in males, two X chromosomes in females. In some mammals, such as the platypus, sex is determined not by one, but by five pairs of sex chromosomes. At the same time, the sex chromosomes of the platypus are more similar to the Z chromosome of birds, and the SRY gene is probably not involved in its sexual differentiation.

Origin and evolution

Before the appearance of the Y chromosome

Recombination inhibition

Ineffective selection

If genetic recombination is possible, the genome of the offspring will differ from the parent. In particular, the genome with fewer harmful mutations can be obtained from parental genomes with a large number harmful mutations.

If recombination is impossible, then if a certain mutation appears, it can be expected that it will appear in future generations, since the process of reverse mutation is unlikely. For this reason, in the absence of recombination, the number of harmful mutations increases over time. This mechanism is called a Möller ratchet.

Part of the Y chromosome (95% in humans) is incapable of recombination. It is believed that this is one of the reasons why she is susceptible to gene damage.

Y chromosome age

Until recently, it was believed that the X and Y chromosomes appeared about 300 million years ago. However, recent research, particularly sequencing of the platypus genome, suggests that chromosomal sex determination was absent as early as 166 million years ago, with the divergence of monotremes from other mammals. This re-evaluation of the age of the chromosomal sex determination system is based on studies showing that sequences on the X chromosome of marsupials and placental mammals are present in the autosomes of the platypus and birds. The older estimate was based on erroneous reports of the presence of these sequences on the platypus X chromosome.

Human Y chromosome

In humans, the Y chromosome consists of more than 59 million base pairs, which is almost 2% of human DNA - in cell nucleus. The chromosome contains just over 86 genes, which encode 23 proteins. The most significant gene on the Y chromosome is the SRY gene, which serves as a genetic “switch” for the development of the body according to the male type. Traits inherited through the Y chromosome are called holandric.

The human Y chromosome is unable to recombine with the X chromosome, except for small pseudoautosomal regions at the telomeres (which make up about 5% of the chromosome length). These are relict areas of ancient homology between the X and Y chromosomes. The main part of the Y chromosome that is not subject to recombination is called NRY. non-recombining region of the Y chromosome) . This part of the Y chromosome allows one to determine direct paternal ancestors through the evaluation of single-nucleotide polymorphisms.

see also

Sources

1. Grützner F, Rens W, Tsend-Ayush E; et al. (2004). “In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes.” Nature. 432 : 913-917. DOI:10.1038/nature03021.
2. Warren WC, Hillier LDW, Graves JAM; et al. (2008). “Genome analysis of the platypus reveals unique signatures of evolution” . Nature. 453 : 175-183. DOI:10.1038/nature06936.
3. Veyrunes F, Waters PD, Miethke P; et al. (2008). “Bird-like sex chromosomes of platypus imply recent origin of mammal sex chromosomes” . Genome Research. 18 : 965-973. DOI:10.1101/gr.7101908.
4. Lahn B, Page D (1999). “Four evolutionary strata on the human X chromosome.” Science. 286 (5441): 964-7. DOI:10.1126/science.286.5441.964. PMID.
5. Graves J.A.M. (2006). “Sex chromosome specialization and degeneration in mammals.” Cell. 124 (5): 901-14. DOI:10.1016/j.cell.2006.02.024. PMID.
6. Graves J. A. M., Koina E., Sankovic N. (2006). “ How the gene content of human sex chromosomes evolved.” Curr Opin Genet Dev. 16 (3): 219-24. DOI:10.1016/j.gde.2006.04.007. PMID.
7. Graves J.A. The degenerate Y chromosome--can conversion save it? (English) // Reproduction, fertility, and development. - 2004. - Vol. 16, no. 5 . - P. 527-534. - DOI:10.10371/RD03096. - PMID 15367368.[to correct ]

This small, at first glance, molecular structure, which appeared almost 300 million years ago, plays the most decisive role not only in the formation of sex, but in all evolution. It is she who is responsible for reproduction, survival and storage of information about the most distant ancestors.

And although the male Y chromosome contains a much smaller number of genes compared to the same X chromosome, only with its help it was possible to preserve the most important characteristics inherent in both stronger sex, and to humanity as a whole.

The main gene is SRY

The most famous gene located on the Y chromosome is rightly considered the SRY gene. Thanks to it, the embryo develops according to the male type - thus, the male genital organs are formed in the fetus. If this gene is damaged, then despite the presence of the Y chromosome, a girl is born instead of a boy.

True, scientists have also recorded the opposite cases, when SRY accidentally got into the X chromosome (female chromosome) and became the cause of the birth of a boy with a full female set (XX).

I would like to remind you that hundreds of millions of years ago, even before the SRY gene entered the male chromosome, the sex of a living creature depended only on environment And natural conditions. A similar development can be observed today in turtles - the birth of females or males from the eggs they lay is determined solely by temperature.

DAZ – guarantee of procreation

Scientists believe that this gene appeared on the male chromosome about 20-40 million years ago, just at the time of the first primates. In their opinion, it is DAZ that is responsible for spermatoginesis – one of the most important functions men.

Accordingly, its damage or absence causes infertility or a low number of viable sperm.

Why are we talking

It turns out that we are also endowed with the ability to verbally express our thoughts thanks to the Y chromosome. Recent studies show that this was facilitated by the special gene PCDHY, which appeared in male cages about 120-200 thousand years ago.

Scientists say that with its help the shell nerve cells began to be formed in a certain way, which significantly simplified the transmission and perception of information.

Survival comes first

It should be noted that the male chromosome is responsible not only for the development and continuation of the species - in addition, it is capable of ensuring survival.

So, according to the latest study by Swedish experts, a decrease in the number of Y chromosomes in white blood cells leads to premature death from various diseases. While a sufficient number of male structures gives a chance to maintain health and live a long life.

The researchers came to this conclusion as a result of many years of monitoring big amount male patients, among whom were older people.

How to look for ancestors

Another important advantage male chromosome is its ability to store genetic information about previous generations. Thus, British scientists have found that people with the same last name very often have similar Y chromosomes. They explain this by the fact that it is men who can preserve both the original surname and the genetic code.

This is why people use Hi-tech, which determine DNA, - with their help, it opens up for them amazing story ancestors and often new relatives are found. They don’t lag behind the lovers of the past modern historians, which reveal no less Interesting Facts about the life of ancient peoples.

A little about disappearance

Just a few years ago, scientists were unanimous and believed that the male chromosome would disappear over time. Such a sad fact was confirmed by the results of numerous studies that showed that during its existence, the Y chromosome lost several hundred genes.

Nevertheless, today's discoveries allow us to look into the future with optimism - after all, as confirmed last works biologists, the decay process has stopped. Thus, according to the famous American scientist David Page, the male chromosome has been stable for the last twenty-five million years. Moreover, its presence guaranteed further evolution.

Well, we, in turn, would like to hope that the main male component will not only remain unchanged, but will also become more perfect - giving new opportunities to the stronger sex and all of humanity.

author: Olga Volkova, for the site

As the now Prime Minister (then President) of Russia Vladimir Putin said in 2006, “if a grandmother had certain sexual characteristics, she would be a grandfather.” The discussion was about the possibility of Russia adopting sanctions against Iran, but the comparison is not entirely correct. Thanks to advances in genetics, we know that a grandmother differs from a grandfather not only in appearance, but also in the set of sex chromosomes.

In most mammals, sex is determined by them: the male body is the carrier of the X- and Y-chromosomes, and women “make do” with two X-chromosomes. Once this division did not exist, but as a result of evolution about 300 million years ago, chromosomes differentiated. There are variations whereby some men's cells contain two X chromosomes and one Y chromosome, or one X chromosome and two Y chromosomes; Some women's cells contain three or one X chromosome. Occasionally, female XY organisms or male XX organisms are observed, but the vast majority of people still have a standard configuration of sex chromosomes. For example, the phenomenon of hemophilia is associated with this feature. The defective gene that impairs blood clotting is linked to the X chromosome and is recessive. For this reason, women only endure the disease without suffering from it themselves due to the presence of a duplicate gene due to the second X chromosome, but men in a similar situation carry only a defective gene and get sick.

One way or another, the Y chromosome has traditionally been considered weak point male organisms, reducing genetic diversity and hindering evolution.

However latest research showed that fears about the extinction of the male race are greatly exaggerated: the Y chromosome does not even think of stagnating.

On the contrary, its evolution is very active, it changes much faster than other areas genetic code person.

Research published in Nature, showed that a specific part of the human Y chromosome and one of its immediate family- chimpanzees are very different. Over the 6 million years of separate evolution of monkeys and humans, the fragment of the chromosome responsible for the production of germ cells has changed by a third or even half. The rest of the chromosome is actually quite constant.

Scientists' assumptions about the conservatism of the Y chromosome were based on objective factors: being transmitted from father to son without changes (for the X chromosome there are as many as three options - two from the mother and one from the father, all of them can exchange genes), it cannot gain genetic diversity from the outside, changing only due to the loss of genes. According to this theory, in 125 thousand years the Y chromosome will finally die out, which could be the end of all humanity.

However, for 6 million years of separate evolution of humans and chimpanzees, the Y chromosome has been successfully changing and progressing. IN new job, held at the Massachusetts Institute of Technology, talks about the chimpanzee's Y chromosome. The human Y chromosome was deciphered in 2003 by the same group led by Professor David Page.

The results of the new study surprised geneticists: they expected that the sequence of genes on the two chromosomes would be very similar.

For comparison: in total mass The DNA of humans and chimpanzees is different in only 2% of genes, and the Y chromosome differs by more than 30%!

Professor Page compared the process of evolution of the male chromosome to a change in the appearance of a house, the owners of which remain the same. “Despite the fact that the same people live in the house, almost constantly one of the rooms is completely updated and renovated. As a result, after a certain period of time, as a result of “room-by-room” renovation, the entire house changes. However, this trend is not normal for the entire genome,” he noted.

The reason for this unexpected instability of the Y chromosome is not yet precisely clear. Scientists suggest that genetic diversity in it is ensured by instability to mutations. The usual mechanism for “repairing” genes fails on the Y chromosome, opening the way for new mutations. Statistically, a larger number of them become fixed and change the genome.

In addition, these mutations are subject to significantly greater selection pressure. This is determined by their function - the production of germ cells. Any beneficial mutations will be fixed with to a greater extent probabilities, since they act directly - increasing the ability of an individual to reproduce. At the same time, ordinary mutations have an indirect effect - increasing the body's resistance to disease or to harsh environmental conditions, for example. Thus, the benefit of a mutation in a nonspecific DNA section will only be revealed if the organism falls into the corresponding unfavourable conditions. In other cases, mutant and non-mutant organisms will perform similarly. Fertility appears very quickly - already in the second generation. An individual either reproduces as a result of mutation more successfully and leaves numerous offspring, or reproduces noticeably worse and cannot increase the share of its genes in the general population. This mechanism functions more efficiently in chimpanzees, whose females constantly mate with a large number of males. As a result, the germ cells enter into direct competition, and “selection” occurs as efficiently as possible. In humans, due to more conservative models of reproduction, the Y chromosome has not evolved so rapidly, geneticists say.

This hypothesis is supported by the fact that the parts of the chromosome involved in sperm production are most different between humans and chimpanzees.

Professor Page's group, in collaboration with the University of Washington Genome Center, continues to work on deciphering the Y chromosome of other mammals. They hope to shed light on the evolution of sex chromosomes and its relationship to population behavior patterns.