Cookies on this website
We use cookies to ensure that we give you the best experience on our website. If you click 'Continue' we'll assume that you are happy to receive all cookies and you won't see this message again. Click 'Find out more' for information on how to change your cookie settings.

The equilibrium per-genome mutation rate in sexual species is thought to result from a trade-off between the benefits of reducing the deleterious mutation rate and the costs of increasing fidelity. We propose that selection will often favour a lower mutation rate on the X chromosome than on autosomes, owing to the exposure of deleterious recessive mutations on hemizygous chromosomes. We tested this hypothesis by examining 33 X-linked genes that have been sequenced in both mouse and rat, and compared their rate of evolution against 238 autosomal genes. The X-linked genes were found to have a significantly lower rate of synonymous substitution than the autosomal genes. Neither the supposed higher mutation rate in males nor stronger purifying selection against slightly deleterious mutations on the X chromosome can account for the low value. The most parsimonious explanation is that rodents have a lower mutation rate on the X chromosome than on autosomes. It is therefore likely that previous indirect estimates of the excess male mutation rate are inaccurate. Indeed, after correction we find no evidence for a male-biased mutation rate in rodents. Furthermore, the rate of synonymous substitution in Y-linked genes is not significantly different from that in autosomal ones. The extent to which enhanced male mutation rates are problematic for the mutational deterministic model of the evolution of sex must, in turn, be questioned.

Original publication

DOI

10.1038/386388a0

Type

Journal article

Journal

Nature

Publication Date

27/03/1997

Volume

386

Pages

388 - 392

Keywords

Animals, Biological Evolution, Female, Genetic Linkage, Germ-Line Mutation, Male, Mice, Models, Genetic, Mutation, Rats, Selection, Genetic, Sex Characteristics, X Chromosome, Y Chromosome