Sex reversal: a fountain of youth for sex chromosomes?
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.
Perrin
Nicolas
N
Department of Ecology and Evolution, University of Lausanne, CH 1015 Lausanne, Switzerland. nicolas.perrin@unil.ch
D000818:Animals; D005075:Biological Evolution; D012734:Disorders of Sex Development; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D010641:Phenotype; D012730:Sex Chromosomes