Newfeld S J, Tachida H, Yedvobnick B
J Mol Evol. 1994 Jun;38(6):637-41. doi: 10.1007/BF00175884.
Interspecific sequence comparison of the highly repetitive Drosophila gene mastermind (mam) reveals extensive length variation in homopolymer domains. The length variation in homopolymers is due to nucleotide misalignment in the underlying triplet repeats, which can lead to slippage mutations during DNA replication or repair. In mam, the length variation in repetitive regions appears to be balanced by natural selection acting to maintain the distance between two highly conserved charge clusters. Here we report a statistical test of the null hypothesis that the similarity in the amino acid distance between the charge clusters of each species arose by chance. The results suggest that at mam there is a juxtaposition of length variability due to molecular drive and length conservation maintained by natural selection. The analysis of mam allows the extension of current theories of drive-selection interaction to encompass homopolymers. Our model of drive-selection equilibrium suggests that the physical flexibility, length variability, and abundance of homopolymer domains provide an important source of genetic variation for natural populations.
高度重复的果蝇基因“主谋”（mam）的种间序列比较显示，同聚物结构域存在广泛的长度变异。同聚物中的长度变异是由于潜在三联体重复序列中的核苷酸错配，这可能导致DNA复制或修复过程中的滑动突变。在mam基因中，重复区域的长度变异似乎通过自然选择来维持两个高度保守电荷簇之间的距离而达到平衡。在这里，我们报告了一个零假设的统计检验，即每个物种电荷簇之间氨基酸距离的相似性是偶然产生的。结果表明，在mam基因中，由于分子驱动导致长度变异性，以及自然选择维持长度保守性这两种情况并存。对mam基因的分析使得当前关于驱动-选择相互作用的理论得以扩展，从而涵盖同聚物。我们的驱动-选择平衡模型表明，同聚物结构域的物理柔韧性、长度变异性和丰度为自然种群提供了重要的遗传变异来源。
