Kliman R M, Hey J
Department of Biological Sciences, Rutgers University, Piscataway, New Jersey 08855-1059.
Genetics. 1994 Aug;137(4):1049-56. doi: 10.1093/genetics/137.4.1049.
Codon bias varies widely among the loci of Drosophila melanogaster, and some of this diversity has been explained by variation in the strength of natural selection. A study of correlations between intron and coding region base composition shows that variation in mutation pattern also contributes to codon bias variation. This finding is corroborated by an analysis of variance (ANOVA), which shows a tendency for introns from the same gene to be similar in base composition. The strength of base composition correlations between introns and codon third positions is greater for genes with low codon bias than for genes with high codon bias. This pattern can be explained by an overwhelming effect of natural selection, relative to mutation, in highly biased loci. In particular, this correlation is absent when examining fourfold degenerate sites of highly biased genes. In general, it appears that selection acts more strongly in choosing among fourfold degenerate codons than among twofold degenerate codons. Although the results indicate regional variation in mutational bias, no evidence is found for large scale regions of compositional homogeneity.
密码子偏好性在黑腹果蝇的基因座间差异很大，其中一些多样性已通过自然选择强度的变化得到解释。一项关于内含子与编码区碱基组成相关性的研究表明，突变模式的变化也导致了密码子偏好性的差异。方差分析（ANOVA）证实了这一发现，该分析表明来自同一基因的内含子在碱基组成上具有相似性的趋势。对于密码子偏好性低的基因，内含子与密码子第三位的碱基组成相关性强度高于密码子偏好性高的基因。这种模式可以通过在高度偏好的基因座中，相对于突变而言自然选择的压倒性作用来解释。特别是，在检查高度偏好基因的四重简并位点时，这种相关性不存在。一般来说，似乎选择在四重简并密码子之间的选择中比在双重简并密码子之间的选择中作用更强。虽然结果表明突变偏好存在区域差异，但未发现组成均匀性的大规模区域的证据。
