Wayne M L, Kreitman M
Department of Ecology and Evolution, University of Chicago, IL 60637, USA.
Genet Res. 1996 Oct;68(2):101-8. doi: 10.1017/s001667230003398x.
In Drosophila melanogaster and closely related species, polymorphism has been shown to be reduced at loci located in regions of low recombination on the X chromosome and on the fourth chromosome, which does not normally recombine. This positive correlation between nucleotide polymorphism level and recombination rate is not predicted by standard neutral theory and therefore must result from natural selection and genetic hitchhiking along the chromosomes. We report here the near-complete absence of variation at concertina (cta), a locus located in the beta-heterochromatic base of chromosome 2L, a region of strongly reduced recombination. A 1.2 kilobase region containing coding regions and introns was sequenced from each of nine lines of D. melanogaster and nine lines of D. simulans representing worldwide collections. Variation is significantly reduced in eta in both species compared with other available loci on the same chromosome. Two analyses of background selection demonstrate that the reduction in variation at cta. considered in combination with other loci on chromosome 2L or alone, is consistent with the background selection model.
在黑腹果蝇及亲缘关系密切的物种中，研究表明位于X染色体低重组区域以及通常不发生重组的第四条染色体上的基因座处的多态性有所降低。核苷酸多态性水平与重组率之间的这种正相关关系并非标准中性理论所预测的，因此必定是由自然选择以及沿染色体的遗传搭便车效应导致的。我们在此报告，位于2L染色体β异染色质基部（一个重组强烈减少的区域）的基因座——风箱基因（cta）几乎完全没有变异。从代表全球样本的黑腹果蝇的9个品系和拟果蝇的9个品系中，分别对包含编码区和内含子的1.2千碱基区域进行了测序。与同一条染色体上的其他可用基因座相比，这两个物种的风箱基因中的变异都显著减少。对背景选择的两项分析表明，风箱基因处变异的减少，无论是结合2L染色体上的其他基因座考虑，还是单独考虑，都与背景选择模型一致。
