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Evolution. 2009 Dec;63(12):3043-9. doi: 10.1111/j.1558-5646.2009.00837.x. Epub 2009 Sep 9.

Sex reversal: a fountain of youth for sex chromosomes?

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Department of Ecology and Evolution, University of Lausanne, CH 1015 Lausanne, Switzerland.


Nonrecombining Y chromosomes are expected to degenerate through the progressive accumulation of deleterious mutations. In lower vertebrates, however, most species display homomorphic sex chromosomes. To address this, paradox I propose a role for sex reversal, which occasionally occurs in ectotherms due to the general dependence of physiological processes on temperature. Because sex-specific recombination patterns depend on phenotypic, rather than genotypic sex, homomorphic X and Y chromosomes are expected to recombine in sex-reversed females. These rare events should generate bursts of new Y haplotypes, which will be quickly sorted out by natural or sexual selection. By counteracting Muller's ratchet, this regular purge should prevent the evolutionary decay of Y chromosomes. I review empirical data supporting this suggestion, and propose further investigations for testing it.

[Indexed for MEDLINE]

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