Ayala F J, Hartl D L
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138.
Mol Biol Evol. 1993 Sep;10(5):1030-40. doi: 10.1093/oxfordjournals.molbev.a040052.
DNA sequences were determined for three to five alleles of the bride-of-sevenless (boss) gene in each of four species of Drosophila. The product of boss is a transmembrane receptor for a ligand coded by the sevenless gene that triggers differentiation of the R7 photoreceptor cell in the compound eye. Population parameters affecting the rate and pattern of molecular evolution of boss were estimated from the multinomial configurations of nucleotide polymorphisms of synonymous codons. The time of divergence between D. melanogaster and D. simulans was estimated as approximately 1 Myr, that between D. teissieri and D. yakuba as approximately 0.75 Myr, and that between the two pairs of sibling species as approximately 2 Myr. (The boss genes themselves have estimated divergence times approximately 50% greater than the species divergence times.) The effective size of the species was estimated as approximately 5 x 10(6), and the average mutation rate was estimated as 1-2 x 10(-9)/nucleotide/generation. The ratio of amino acid polymorphisms within species to fixed differences between species suggests that approximately 25% of all possible single-step amino acid replacements in the boss gene product may be selectively neutral or nearly neutral. The data also imply that random genetic drift has been responsible for virtually all of the observed differences in the portion of the boss gene analyzed among the four species.
测定了果蝇四个物种中每个物种的七无新娘（boss）基因的三到五个等位基因的DNA序列。boss的产物是一种跨膜受体，用于结合由七无基因编码的配体，该配体触发复眼中R7光感受器细胞的分化。根据同义密码子的核苷酸多态性的多项配置，估计了影响boss分子进化速率和模式的群体参数。黑腹果蝇和拟果蝇之间的分歧时间估计约为100万年，泰氏果蝇和雅库布果蝇之间的分歧时间约为75万年，这两对姊妹物种之间的分歧时间约为200万年。（boss基因本身的估计分歧时间比物种分歧时间大约大50%。）物种的有效大小估计约为5×10⁶，平均突变率估计为1-2×10⁻⁹/核苷酸/代。物种内氨基酸多态性与物种间固定差异的比率表明，boss基因产物中所有可能的单步氨基酸替换中约25%可能是选择性中性或近中性的。数据还表明，随机遗传漂变几乎导致了四个物种中分析的boss基因部分中观察到的所有差异。
