MODELS OF NEARLY NEUTRAL MUTATIONS WITH PARTICULAR IMPLICATIONS FOR NONRANDOM USAGE OF SYNONYMOUS CODONS
MODELS OF NEARLY NEUTRAL MUTATIONS WITH PARTICULAR IMPLICATIONS FOR NONRANDOM USAGE OF SYNONYMOUS CODONS
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DOI：
10.1007/bf02134132
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发表时间：
1987-01-01
影响因子：
3.9
通讯作者：
LI, WH
中科院分区：
文献类型：
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作者：
LI, WH
使用单位点和多位点模型研究近中性突变的群体动态。在后一种模型中，序列中的核苷酸是完全连接的，并且采用的选择方案是加法、乘法和具有阈值的加法。尽管第三种选择方案与前两种方案有很大不同，但这三种方案对于各种参数值都产生相同的结果。因此，本研究为近中性突变的群体动态提供了一般理论，因为结果也可用于推断其他选择方案，例如稳定选择和协同选择。结果表明，在多位点模型下，序列中积累的轻微有害突变的数量可能比单位点模型下的要大得多，特别是如果序列很长或每个位点的突变率很高。结果表明，即使同义密码子之间非常微小的选择性差异也会在密码子使用中产生强烈的偏差。对于细菌和酵母基因中密码子使用的强烈偏差，考虑了三种替代解释。讨论了当前结果对分子进化的影响。
The population dynamics of nearly neutral mutations are studied using a single-site and a multisite model. In the latter model, the nucleotides in a sequence are completely linked and the selection schemes employed are additive, multiplicative, and additive with a threshold. Although the third selection scheme is very different from the first two, the three schemes produce identical results for a wide range of parameter values. Thus the present study provides a general theory for the population dynamics of nearly neutral mutations because the results can also be used to draw inferences about other selection schemes such as stabilizing selection and synergistic selection. It is shown that the number of slightly deleterious mutations accumulated in a sequence can be considerably larger under the multisite model than under the single-site model, particularly if the sequence is long or if the mutation rate per site is high. The results show that even a very slight selective difference between synonymous codons can produce a strong bias in codon usage. Three alternative explanations for the strong bias in codon usage in bacterial and yeast genes are considered. The implications of the present results for molecular evolution are discussed.