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Our Genome Has Adopted Virus Genes Critical to Our Survival

Thu, 02/16/2012 - 2:21am
Curious Cat Science and Engineering Blog

Mammals Made By Viruses by Carl Zimmer

Viruses have insinuated themselves into the genome of our ancestors for hundreds of millions of years. They typically have gotten there by infecting eggs or sperm, inserting their own DNA into ours. There are 100,000 known fragments of viruses in the human genome, making up over 8% of our DNA. Most of this virus DNA has been hit by so many mutations that its nothing but baggage our species carries along from one generation to the next. Yet there are some viral genes that still make proteins in our bodies. Syncytin appeared to be a hugely important one to our own biology. Originally, syncytin allowed viruses to fuse host cells together so they could spread from one cell to another. Now the protein allowed babies to fuse to their mothers.

The big picture thats now emerging is quite amazing. Viruses have rained down on mammals, and on at least six occasions, theyve gotten snagged in their hosts and started carrying out the same function: building placentas.

Some mammals that scientists have yet to investigate, such as pigs and horses, dont have the open layer of cells in their placenta like we do. Scientists have come up with all sorts of explanations for why that may be, mainly by looking for differences in the biology of each kind of mammals. But the answer may be simpler: the ancestors of pigs and horses might never have gotten sick with the right virus.

More amazing facts from science. This stuff is so interesting. Carl Zimmer is a fantastic science writer and he has written several great science books.

Related: Amazing Science, RetrovirusesMicrocosm by Carl ZimmerTen Things Everyone Should Know About ScienceParasite Rex

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