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Ancient virus determines babies' sex
NEW HAVEN, Conn., March 31 (UPI) -- Over the course of human evolution, the human genome has picked up foreign fragments of DNA, mostly from ancient viruses.
The majority of those fragments are inactive, but a few serve novel purposes -- like determining the sex of a developing embryo.
Yale researchers believe an ancient viral DNA strand -- incorporated into the mammalian genome as recently as 1.5 million years ago -- plays a key role in turning off the X chromosome.
Scientists at Yale University determined that some embryos turn off the virus on the X chromosome, affecting sex ratios, and discovered the mechanism by which they do it. In the epigenetic marker they found, a methyl bond is added to adenine, one of the four nucleotides that form DNA base pairs, producing a gene-silencing ability.
Source: UPI