The Role of Chance in Adaptation

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Omai's picture
The Role of Chance in Adaptation

Check out this blog by Aaron Hirsh in the New York Times about the role of chance in adaptation and evolution focusing on the fields of animal behavior, immunology, and sexual reproduction. A great read.
Here is the link:
The blog also includes references to some neat papers (especially the one on cockroaches!)

R Bishop
R Bishop's picture
There was a cool article this

There was a cool article this week in PLoS Biology where the authors showed that areas of the genome that are "hotspots" of forward change in protein coding are NOT A MATTER OF NATURAL SELECTION.  Rather the rate of mutation is simply driven by a bias of G/C for A/T base pair changes at those spots.  So much for Darwin. Hopefully I can find to dissect this manuscript a bit and see if makes sense.  Might be a fun one to do in Journal Club. hint hint!
Hotspots of Biased Nucleotide Substitutions in Human Genes
Authors summary : Regions of the human genome that appear to evolve rapidly may have been under strong positive selection and could contain the genetic changes responsible for the uniqueness of our species. However, neutral (nonadaptive) evolutionary processes can give rise to signals that can be mistaken as signs of selection. In this article, we identify coding sequences that have undergone accelerated rates of change in humans, affecting the divergence of the proteins they encode. By analyzing patterns of molecular evolution in these genes and their distribution in the genome, we show that many protein-coding changes in the fastest-changing genes are not a result of selection operating on the genes, but instead result from biased fixation of AT-to-GC mutations. Our findings are consistent with a model of recombination-driven biased gene conversion. This leads to the provocative hypothesis that many of the genetic changes leading to human-specific characters may have been prompted by fixation of deleterious mutations.
Citation: Berglund J, Pollard KS, Webster MT (2009) Hotspots of Biased Nucleotide Substitutions in Human Genes. PLoS Biol 7(1): e1000026 doi:10.1371/journal.pbio.1000026