Carl Zimmer explains current thinking on the origins of mitochondria

That title may not sound interesting to most, but I find the topic fascinating. In his latest blog entry, Zimmer expounds on how a viral infection might have played a signficant role in the symbiotic process through which bacterial mitochodria ancestors became an essential part of our (and all eukaryotes) genome.

Here’s the history as they now see it: the free-living, oxygen-breathing ancestors of mitochondria were infected with some nasty T3/T7 viruses. Most of the time the viruses were fatal. But some mutant tried to replicate itself inside a proto-mitochondrion and failed. Its genes were trapped in the genome of its host. Its host was able to reproduce, and one of its descendants took up residence inside the cell of a eukaryote. At some point after this merger, a mutation caused the virus’s DNA and RNA copying genes to come back online. They took over the job of making these molecules, and the mitochondria’s own genes for this job were later stripped out of its genome.