Concerted evolution is a process in which related genes within a species undergo genetic exchange, causing their sequence evolution to be concerted over some period of time. The best known example of concerted evolution is among multicopy rDNA genes in animals. Analysis in the Thomas lab focuses on smaller protein-coding gene families that appear to undergo concerted evolution.
Detecting concerted evolution
Naively, detecting genes that undergo concerted evolution is as simple as identifying closely-related paralogous genes. Indeed, there is a long and checkered history of exactly this approach. More recently it has become clear that a combination of high rates of gene duplication and strong purifying selection explain many cases previously thought to result from concerted evolution. The primary method that we have used to detect concerted evolution depends on comparing paralog groups between two or more related species (see Figure).
Implications of concerted evolution
We got interested in concerted evolution from a back door, which was opened by analysis of the mechanism of gene duplication. Nearly all primary gene duplication events in C. elegans appear to occur locally, resulting in adjacent or nearly-adjacent copies of initially identical genes. One study showed that these local duplicates appear to be approximately evenly split between pairs in the same genomic orientation and those in opposite orientation. This was puzzling, since the most obvious way to generate gene duplications is by unequal crossing over, which will always generate duplicates in the same orientation. Our work has shown that most, possibly all, cases of apparent recent duplications in opposite orientation are actually older gene pairs that are undergoing concerted evolution. This concerted evolution makes the pair of genes appear to result from a recent duplication, when in fact their high sequence similarity is maintained by intergenic sequence exchange.
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