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You can also add newsletters iflscience. IFLScience needs the contact information you provide to us to contact you about our products and services. You may unsubscribe from these communications at any time. For information on how to unsubscribe, as well as our privacy practices and commitment to protecting your privacy, check out our Privacy Policy. The Y chromosome may be a symbol of masculinity, but it is becoming increasingly clear that it is anything but strong and enduring.
Women, after all, manage just fine without one. If the same rate of degeneration continues, the Y chromosome has just 4.
If we rewind the clock to m years ago, to the very first mammals, the story was completely different. However, Y chromosomes have a fundamental flaw. Unlike all other chromosomes, which we have two copies of in each of our cells, Y chromosomes are only ever present as a single copy, passed from fathers to their sons. Deprived of the benefits of recombination, Y chromosomal genes degenerate over time and are eventually lost from the genome. Looking to other species Y chromosomes exist in mammals and some other species , a growing body of evidence indicates that Y-chromosome gene amplification is a general principle across the board.
These amplified genes play critical roles in sperm production and at least in rodents in regulating offspring sex ratio. Writing in Molecular Biology and Evolution recently, researchers give evidence that this increase in gene copy number in mice is a result of natural selection.