What with the threat of bird flu, the reality of HIV, and the general unseemliness of having one's cells pressed into labour on behalf of something alien and microscopic, it is small wonder that people don't much like viruses. But it's possible that we may actually have something to thank the little parasites for. They may have been the first creatures to find a use for DNA, a discovery that set life on the road to its current rich complexity...
This feature in Nature (by me; registration required) looks at Patrick Forterre's idea that viruses invented DNA as a way of invading cells in the RNA world — just as many viruses today use similar genetic tricks to evade cellular defences. It's a neat idea, and raises the useful question of what the original advantage of DNA might have been. It is more chemically stable than RNA (which biologists think came first) and can be used for longer genomes.
But, Forterre points out, no cell could know that it wanted a longer, more complex genome and evolve DNA accordingly, because evolution has no foresight. Not everyone agrees, but there is a lot of excitement about viral diversity and evolution at the moment - there's some crazy stuff out there, virus-wise, much of it currently being discovered by David Prangishvili.
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