Innan H, Tajima F
Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Japan.
Genetics. 1997 Nov;147(3):1431-44. doi: 10.1093/genetics/147.3.1431.
The amounts of nucleotide variation within and between allelic classes were studied. The expectation and variance of the number of segregating sites and the expectation of the average number of pairwise differences among a sample of DNA sequences were obtained by using the theory of gene genealogy with no recombination. When the ancestral allelic class is unknown, it was found that the amount of variation within an allelic class increases with its frequency in the sample, while the amount of variation between two allelic classes is the largest when the two allelic classes exist equally. On the other hand, if we know the ancestral allelic class, as the frequency of the mutant allelic class increases, the amounts of variation within the mutant allelic class and between two allelic classes increase and the amount of variation within the ancestral allelic class decreases. As an example, we analyzed the polymorphism in the ND5 gene of Drosophila melanogaster and constructed the common ancestral sequence with high confidence, suggesting that the pattern of polymorphism within species gives useful information to know the ancestral sequence of the species.
研究了等位基因类内和类间的核苷酸变异量。利用无重组的基因谱系理论，得到了DNA序列样本中分离位点数量的期望和方差以及成对差异平均数的期望。当祖先等位基因类未知时，发现等位基因类内的变异量随其在样本中的频率增加而增加，而当两个等位基因类等量存在时，两个等位基因类间的变异量最大。另一方面，如果我们知道祖先等位基因类，随着突变等位基因类频率的增加，突变等位基因类内和两个等位基因类间的变异量增加，而祖先等位基因类内的变异量减少。例如，我们分析了黑腹果蝇ND5基因的多态性，并高可信度地构建了共同祖先序列，这表明物种内的多态性模式为了解该物种的祖先序列提供了有用信息。
