Bachtrog Doris
Division of Biological Sciences, University of California, San Diego, 9500 Gilman Drive, MC 0116, La Jolla, CA 92093, USA.
J Mol Evol. 2007 May;64(5):586-90. doi: 10.1007/s00239-006-0257-x. Epub 2007 Apr 24.
Biased codon usage in many species results from a balance among mutation, weak selection, and genetic drift. Here I show that selection to maintain biased codon usage is reduced in Drosophila miranda relative to its ancestor. Analyses of mutation patterns in noncoding DNA suggest that the extent of this reduction cannot be explained by changes in mutation bias or by biased gene conversion. Low levels of variability in D. miranda relative to its sibling species, D. pseudoobscura, suggest that it has a much smaller effective population size. Reduced codon usage bias in D. miranda may thus result from the reduced efficacy of selection against newly arising mutations to unpreferred codons.
许多物种中密码子使用偏好是由突变、弱选择和遗传漂变之间的平衡导致的。在这里我表明，相对于其祖先，拟暗果蝇中维持密码子使用偏好的选择作用减弱。对非编码DNA突变模式的分析表明，这种减弱的程度无法用突变偏好的变化或偏向性基因转换来解释。相对于其近缘物种伪暗果蝇，拟暗果蝇的变异性较低，这表明它的有效种群规模要小得多。因此，拟暗果蝇中密码子使用偏好的降低可能是由于对新出现的非偏好密码子突变的选择效率降低所致。
