Abstract
Population genetics models show that, under certain conditions, the X chromosome is expected to be under more efficient selection than the autosomes. This could lead to 'faster-X evolution', if a large proportion of mutations are fixed by positive selection, as suggested by recent studies in Drosophila. We used a multispecies approach to test this: Muller's element D, an autosomal arm, is fused to the ancestral X chromosome in Drosophila pseudoobscura and its sister species, Drosophila affinis. We tested whether the same set of genes had higher rates of non-synonymous evolution when they were X-linked (in the D. pseudoobscura/D. affinis comparison) than when they were autosomal (in Drosophila melanogaster/Drosophila yakuba). Although not significant, our results suggest this may be the case, but only for genes under particularly strong positive selection/weak purifying selection. They also suggest that genes that have become X-linked have higher levels of codon bias and slower synonymous site evolution, consistent with more effective selection on codon usage at X-linked sites.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Drosophila / classification*
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Drosophila / genetics*
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Drosophila Proteins / genetics
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Evolution, Molecular*
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Female
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Genes, Insect / genetics*
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Genes, X-Linked / genetics*
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Male
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Molecular Sequence Data
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Sequence Analysis, DNA
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Species Specificity
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X Chromosome / genetics
Associated data
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