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It’s a boy! Or maybe it’s a girl, but either way, new research suggests that the sex of mouse babies, and perhaps the sex of human babies, may be influenced by a newfound way to deactivate ancient viral genes that have been embedded in mammal genomes for more than a million years.
In the research, the scientists looked at viral DNA that is active in the mouse genome. Viral DNA can become part of an animal’s genome when a kind of virus called a retrovirus infects a cell, and slips its genes into the DNA of host cells. (The most notorious retrovirus is HIV, the virus behind AIDS.)
If a retrovirus infects a sperm or egg cell — and that sperm or egg is involved in fertilization and becomes part of a person — all of the person’s cells will have the viral DNA, and they will pass it on to their descendants. Hence, people and animals today carry in their cells the genetic remnants of viruses that invaded the genomes of their ancestors.
In fact, more than 40 percent of the human genome may be composed of viral “leftovers,” said Andrew Xiao, the senior author of the new study and a molecular biologist at the Yale School of Medicine in New Haven, Connecticut.
Read full, original post: It’s a Girl! Ancient Viral Genes May Determine a Baby’s Sex