Friday, November 20, 2015

Meeting Nov 24th: sex-bias, X-linkage, and rates of evolution

Posted by Jessica Abbott

D. melanogaster. Photo by Qinyang Li.
Although a number of members of the group are currently away, I thought it would be nice to have a meeting next week anyway. I don't think anyone else has planned anything, so I figured I might as well take the initiative. I suggest that we read the following short paper on the "faster-X effect" - how sex-biased gene expression and X-linkage affect rates of evolution.

Title: The effects of sex-biased gene expression and X-linkage on rates of adaptive protein sequence evolution in Drosophila

Abstract: A faster rate of adaptive evolution of X-linked genes compared with autosomal genes may be caused by the fixation of new recessive or partially recessive advantageous mutations (the Faster-X effect). This effect is expected to be largest for mutations that affect only male fitness and absent for mutations that affect only female fitness. We tested these predictions in Drosophila melanogaster by using genes with different levels of sex-biased expression and by estimating the extent of adaptive evolution of non-synonymous mutations from polymorphism and divergence data. We detected both a Faster-X effect and an effect of male-biased gene expression. There was no evidence for a strong association between the two effects—modest levels of male-biased gene expression increased the rate of adaptive evolution on both the autosomes and the X chromosome, but a Faster-X effect occurred for both unbiased genes and female-biased genes. The rate of genetic recombination did not influence the magnitude of the Faster-X effect, ruling out the possibility that it reflects less Hill–Robertson interference for X-linked genes.

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