Viruses and HGT

To me, perhaps the most interesting thing in evolution is horizontal gene transfer (HGT), also known as lateral gene transfer. Simply put HGT is the process where genes move between organisms in a manner different to being passed on from parent to child, vertical gene transfer.
For one thing it demonstrates that evolution is focused on the level of the gene, the premise of Dawkin’s book The Selfish Gene, because it shows that genes are able to move between genomes and organisms are just environments for them.
It’s also very different to the way we generally think of genes behaving and allows for far more evolutionary flexibility as genes are able to move between vastly different organisms, such as viruses and humans. As a normal part of their life cycle some viruses do insert their own DNA into our genomes. Usually, viruses are bad for us but that isn’t always the case and HGT can carry benefits. There is a piece by Carl Zimmer on The Loom describing how a gene acquired, multiple times, from viruses has become essential for placenta formation.

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