Experts estimate that in 4.5 to 11 million years, the Y chromosome could effectively cease to exist. At the heart of this issue is an understanding of how sex is determined in humans and other mammals.
As a result, the Y chromosome has been slowly losing its genetic material over time, raising concerns about its future viability. If the trend continues, the Y chromosome could eventually become extinct, which would have profound implications for human reproduction and the survival of the male sex.
"This significant gene loss over the centuries has lead scientists to predict that the Y chromosome might vanish entirely in about 11 million years," said Earth.com.
The Y chromosome used to be the same size as the X chromosome 166 million years ago. It's since shrunk to just a third of the size with only about 55 genes compared to the X chromosome's 900 genes. If we extrapolate from the rate it is shrinking, it'll be completely gone in less than 5 million years.
While women have two X chromosomes, men have an X and a Y. But many men begin to lose their Y chromosome in a fraction of their cells as they age. This appears to be particularly true for smokers. The loss occurs predominantly in cells that undergo rapid turnover, such as blood cells.
In turn, this must mean the Y chromosome has lost 900–55 active genes over the 166 million years that humans and platypus have been evolving separately. That's a loss of about five genes per million years. At this rate, the last 55 genes will be gone in 11 million years.
Marshall Graves, a distinguished Professor of Genetics and Vice Chancellor's Fellow, the Y chromosome is "running out of time." If this trend continues, the Y chromosome could disappear entirely within 11 million years, raising fears about the future of male offspring and human survival.
The frequency of the XX male syndrome is approximately 1 in 25,000 males. Since 46,XX males often have normal male external genital development, they typically seek medical attention for delayed puberty, infertility, or gynecomastia. On physical examination, the testes are usually small.
An individual with an X chromosome that carries the SRY gene will develop as a male despite not having a Y chromosome, but will not be able to produce sperm to father biological children.
Z chromosome: A sex chromosome in certain animals, such as chickens, turkeys, and moths. In humans, males are XY and females XX, but in animals with a Z chromosome, males are ZZ and females are WZ.
Are scientists saying the Y chromosome is disappearing?
The human Y chromosome, which contains the SRY gene responsible for male development, has been degenerating over time. Scientists estimate that at the current rate of gene loss, the Y chromosome could vanish entirely within 11 million years.
The XYY syndrome correlates with certain physical conditions and disabilities in males with the extra Y chromosome. Symptoms range from mild to severe, so the physical symptoms can go undetected: Asthma. Autism spectrum disorder.
Even in monotreme mammals, like platypuses and echidnas, XY chromosomes are ordinary. Within the last 166 million years, the human Y chromosome has lost most of its 1,600 genes at a rate of nearly 10 per million years. At this pace, the Y chromosome is expected to vanish in about 4.5 million years.
Males with XYY syndrome have 47 chromosomes because of the extra Y chromosome. This condition is also sometimes called Jacob's syndrome, XYY karyotype, or YY syndrome. The Y chromosome is present in males, who have one X and one Y chromosome, while females have two X chromosomes.
No. The Y chromosome is shrinking because it mostly does not swap genetic material with the X chromosome during meiosis (known as crossing over) which in addition to mixing genetic material for sexual reproduction, is also important for DNA repair.
If the egg receives another X chromosome from the sperm, the resulting individual is XX, forms ovaries, and is female; if the egg receives a Y chromosome from the sperm, the individual is XY, forms testes, and is male. The Y chromosome carries a gene that encodes a testis-determining factor.
Usually, a female baby has 2 X chromosomes (XX) and a male has 1 X and 1 Y (XY). But in Klinefelter syndrome, a boy is born with an extra copy of the X chromosome (XXY). The X chromosome is not a "female" chromosome and is present in everyone. The presence of a Y chromosome denotes male sex.
Over time, mutations accumulate, and some genes are lost. Evolutionary pressures that render some genes redundant have also contributed to its degradation. No one knows for sure why this is happening, but it might be because the Y chromosome is kind of lonely.
The first estimate on prevalence of 46,XY females is 6.4 per 100 000 live born females. The presentation of AIS and gonadal dysgenesis is distinctly different, with AIS being diagnosed during childhood and gonadal dysgenesis during pubertal years. The presenting phenotype is dependent on the cause of 46,XY DSD.
Because the gonads are dysgenetic and nonfunctional, spontaneous pubertal development seldom occurs in these women (12), and successful pregnancy is even more unusual; unassisted pregnancy is unheard of (1).
The most common cause of 46 XX DSD is congenital adrenal hyperplasia (CAH). CAH is a serious medical condition which can be associated with severe electrolyte (such as sodium) imbalances. 46 XX DSD can also result from exposure of the fetus to high levels of male hormones while in utero.
In Swyer syndrome, individuals have one X chromosome and one Y chromosome in each cell, which is the pattern typically found in boys and men; however, they have female reproductive structures . People with Swyer syndrome have female external genitalia and some female internal reproductive structures.
Is it true that the Y chromosome is going extinct?
The Y chromosome, critical for male sex determination, has been losing genetic material and might vanish in the future. Studies in some rodents indicate that species can survive by evolving new sex-determining genes. This suggests the human race might adapt similarly.
Since 2010, scientists have known that the Y chromosome is rapidly evolving in humans, but a new study shows that the same can be said across all Great Apes—the closest relatives to humans.
The researchers calculate that the Y chromosomes carried by modern men are versions of the Y chromosome carried by a common ancestor who lived in Africa about 59,000 years ago, they report in the November issue of Nature Genetics.
