Gene loss on Y chromosomes: a consequence of purifying selection?
Recombination restriction between evolving sex chromosomes leads to the degeneration of the chromosome that is present only in the heterogametic sex (the Y chromosome in XY species). The evolutionary forces driving Y chromosome degeneration, however, are still under debate and include positive and negative selection models. In a recent study, we showed that the rate of accumulation of loss-of-function mutations on the neo-Y chromosome of Drosophila miranda is compatible with the process of Muller's ratchet, the stochastic loss of the best mutational class of individuals from a small asexual population. Purifying selection at amino acid sites can accelerate the ratchet, and the speed of degeneration depends on the number of genes still present on the evolving Y chromosome. Our study shows that Y chromosome degeneration does not require the action of selective sweeps at linked sites, and can take place under realistic parameters of purifying selection only.
Kaiser
Vera B
VB
Center for Theoretical Evolutionary Genomics, University of California, Berkeley, CA, USA. vera.kaiser@berkeley.edu
D000818:Animals; D004330:Drosophila / Q000235:genetics*; D019143:Evolution, Molecular; D017353:Gene Deletion; D008957:Models, Genetic; D009154:Mutation; D012641:Selection, Genetic; D014998:Y Chromosome / Q000235:genetics*