Syncytin Placenta Gene Came Viral

The gene responsible for helping build the mammalian placenta originated from a virus. More than 100 million years ago, a retrovirus infected one of our distant ancestors and inserted its genetic material into the host's DNA. Instead of disappearing over time, the viral gene that encoded a cell-fusion protein was preserved and eventually repurposed by evolution. Today, that gene, known as syncytin, helps fuse cells together to form part of the placenta, making it possible for a mother and fetus to remain physically connected during pregnancy.

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