Thursday, September 08, 2005

Chimp Genome: A glimpse into how evolution works

I've glossed over the article in last week's Nature of the Pan troglodytes (Chimpanzee) genome. By comparing our DNA sequence with that of a species that had a common ancestor a hand full of million years ago we can see how our genome has changed since the split. A good chunk of the paper describes all these DNA elements that have been jumping, replicating and dying slow deaths inside of our DNA. Our chromosomes are literally zoos!

I won't give you a summary ... go visit Pharyngula for the score card.

One interesting finding is that certain alleles (version of a gene) that are associated with disease are the only version found in Chimps! For example the version of the PPAR Gamma gene (a gene that encodes a receptor on the surface of cells ... I think?) that is associated with type 2 diabetes is the only version of the gene found in chimps. What probably happened is that as we split both humans and chimps had the diabetes version, with no diabetes. As other genes changed in humans, due to selection pressures, PPAR-Gamma's function was slightly impaired in the new environment and thus caused diabetes with a higher frequency. Mutant versions of PPRA-Gamma appeared and alleviated these problems. Now the old version of PPAR-Gamma is in the population and is in the course of being selected against (as individuals with the old allele are on average less healthy and have fewer surviving descendents). Evolution at work!