The Y chromosome: beyond gender determination

by Roseanne F. Zhao, Ph.D. NIH M.D./Ph.D. Partnership Training program Scholar

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The person is organized right into 23 pairs of chromosomes (22 pairs of autosomes and one pair of sex chromosomes), with each parental contributing one chromosome per pair. The X and Y chromosomes, additionally known together the sex chromosomes, determine the biological sex of an individual: females inherit an X chromosome indigenous the father for a XX genotype, while males inherit a Y chromosome native the father for a XY genotype (mothers just pass top top X chromosomes). The existence or lack of the Y chromosome is critical because it includes the genes crucial to override the biological default - female breakthrough - and cause the advance of the male reproductive system. although the Y chromosome"s role in sex determination is clear, research study has shown that that is undergoing fast evolutionary deterioration. Numerous generations earlier the Y chromosome was large, and also contained as countless genes together the X chromosome. Now it is a portion of its past size and contains fewer than 80 useful genes. This has led to debates and concerns end the years regarding the Y chromosome"s eventual destiny. Numerous speculate that the Y chromosome has come to be superfluous and could totally decay in ~ the following 10 million years. While researches of the Y chromosome have been complicated due to the palindromic and repeat-rich nature of its DNA sequence, recent genomic developments have provided some unforeseen insights. This installment of the breakthrough of the Month highlights two studies released in the April 24, 2014, problem of Nature that check out the evolutionary path of the Y chromosome in miscellaneous mammals. Together, this studies show the security of the Y chromosome end the past 25 million years. They more reveal some crucial functions the the Y chromosome that imply it may be right here to stay. To get started, let"s first delve right into the evolutionary beginning of the sex chromosomes, approximately 200-300 million years ago. The X and also Y chromosomes, both that which acquired from autosomes, to be initially about the very same size. In ~ some particular time along the way, the Y chromosome progressively lost the capacity to recombine - or exchange hereditary information - v the X chromosome and also began to evolve independently. This quickly led come a catastrophic deterioration of the Y chromosome, i beg your pardon now contains only 3 percent the the genes that it once mutual with the X chromosome.  Recent work from the research groups of David C. Page, M.D., in ~ the whitehead Institute, Massachusetts academy of Technology, and also Henrik Kaessmann, Ph.D., in ~ the Swiss academy of Bioinformatics and also the university of Lausanne in Switzerland, suggests that the at first rapid decrease of the Y chromosome may have leveled off and stabilized. Using different genomic technologies, these two research study teams analyzed the advancement of the Y chromosome independently in two separate sets of mammals that covered an ext than 15 various species, including humans, chimpanzees, rhesus monkeys, bulls, marmosets, mice, rats, dogs and opossums. Strikingly, they discovered a tiny but stable team of crucial regulatory gene on the Y chromosome the have withstood over a lengthy evolutionary duration of time, also while surrounding genes to be decaying. Significantly, these genes play a critically important duty in administrate the expression of other genes throughout the and may influence tissues transparent the human being body. Among the factors for the continued endurance of these regulatory Y chromosome gene is the they space "dosage-dependent," definition that two duplicates are forced for common function.  For many genes ~ above the X-chromosome, just one copy is required. Females have actually two X chromosomes and therefore two copies of every X-linked gene, so one copy is randomly inactivated, or turned off. Males have actually only one X chromosome and therefore only one copy is expressed.  However, regulatory genes are often dosage-dependent and haplo-insufficient, i.e., two copies of the gene space required and also the existence of just one copy can lead come abnormalities or disease. In females, this regulatory gene escape X-inactivation so that the copy top top the second X chromosome is also expressed; in males, who only have actually one X chromosome, the preservation of this team of regulatory genes on the Y chromosome is an essential for offering the 2nd copy.  Overall, what this means is that beyond its duty in sex determination and fertility, the Y chromosome additionally contains crucial genes that are an essential for the health and also survival the males. these findings have considerable implications for our understanding of differences in biology, health and disease between men and women. Because genes top top the X and also Y chromosomes have a history of an option independent of every other, ethereal functional distinctions may exist that space a direct consequence of genetic distinctions on the 2 chromosomes.

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While these differences have no yet to be explored in great detail, more studies on the conserved Y chromosome gene can help us to understand differences in the simple biology and susceptibility to illness in men and also women and better guide health and wellness management. Review the articles: