The molecular clock revisited: the rate of synonymous vs. replacement change in Drosophila
The molecular clock revisited: the rate of synonymous vs. replacement change in Drosophila
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重新审视分子钟：果蝇中同义变化与替代变化的比率
DOI：
10.1023/a:1017035109224
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发表时间：
2004
期刊：
影响因子：
1.5
通讯作者：
M. Kreitman
中科院分区：
文献类型：
--
作者：
L. Zeng;J. M. Comeron;Bin Chen;M. Kreitman
研究了果蝇属3种果蝇中24个基因的同义和非同义替换率。pseudobscura、拟暗纹叶蝉D. subobscura和D.黑腹菌D. pseudoobscura和D. subobscura是obscura进化枝的两个远亲成员，平均每个位点相差0.29个同义核苷酸取代。D. melanogaster与两个obscura物种的不同之处在于每个位点平均0.81个同义替换。使用由吉莱斯皮开发的方法，我们研究了三个物种的分支沿着取代的方差与平均值之比，或分散指数R，以测试分子进化中性理论的基本预测，E（R）= 1。对于非同义替换，平均R，Ra为1.6，这与中性理论预测没有显著差异。24个基因中只有5个具有显著大的Ra值，12个基因的Ra估计值小于1。相比之下，对于24个基因中的12个，同义替换的分散指数显著较大，平均Rs = 4.4，也具有统计学显著性。这些研究结果与哺乳动物的结果，这表明过度分散的非同义取代，但不是同义取代。弱选择作用，以维持密码子的偏好在果蝇，但不是在哺乳动物中，可能是重要的解释在这组生物体的同义替换率的高方差。
Rates of synonymous and nonsynonymous substitution were investigated for 24 genes in three Drosophila species, D. pseudoobscura, D. subobscura, and D. melanogaster. D. pseudoobscura and D. subobscura, two distantly related members of the obscura clade, differ on average by 0.29 synonymous nucleotide substitutions per site. D. melanogaster differs from the two obscura species by an average of 0.81 synonymous substitutions per site. Using a method developed by Gillespie, we investigated the variance to mean ratio, or Index of Dispersion, R, of substitutions along the three species' branches to test the fundamental prediction of the neutral theory of molecular evolution, E(R) = 1. For nonsynonymous substitutions, the average R, Ra is 1.6, which is not significantly different from the neutral theory prediction. Only 5 of the 24 genes had significantly large Ra valves, and 12 of the genes had Ra estimates of less than one. In contrast, the Index of Dispersion for synonymous substitutions was significantly large for 12 of the 24 genes, with an average of Rs = 4.4, also statistically significant. These findings contrast with results for mammals, which showed overdispersion of nonsynonymous substitutions, but not of synonymous substitutions. Weak selection acting to maintain codon bias in Drosophila, but not in mammals, may be important in explaining the high variance in the rate of synonymous substitutions in this group of organisms.
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DOI：
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发表时间：
1996-07-09
影响因子：
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