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首页> 外文期刊>Journal of genetics >Nucleotide variation at the dopa decarboxylase (Ddc) gene in natural populations of Drosophila melanogaster
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Nucleotide variation at the dopa decarboxylase (Ddc) gene in natural populations of Drosophila melanogaster

机译：果蝇自然种群中多巴脱羧酶（Ddc）基因的核苷酸变异。

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摘要

We studied nucleotide sequence variation at the gene coding for dopa decarboxylase (Ddc) in seven populations of Drosophila melanogaster. Strength and pattern of linkage disequilibrium are somewhat distinct in the extensively sampled Spanish and Raleigh populations. In the Spanish population, a few sites are in strong positive association, whereas a large number of sites in the Raleigh population are associated nonrandomly but the association is not strong. Linkage disequilibrium analysis shows presence of two groups of haplotypes in the populations, each of which is fairly diverged, suggesting epistasis or inversion polymorphism. There is evidence of two forms of natural selection acting on Ddc. The McDonalda€“Kreitman test indicates a deficit of fixed amino acid differences between D. melanogaster and D. simulans, which may be due to negative selection. An excess of derived alleles at high frequency, significant according to the e???-test, is consistent with the effect of hitchhiking. The hitchhiking may have been caused by directional selection downstream of the locus studied, as suggested by a gradual decrease of the polymorphism-to-divergence ratio. Altogether, the Ddc locus exhibits a complicated pattern of variation apparently due to several evolutionary forces. Such a complex pattern may be a result of an unusually high density of functionally important genes.
机译：我们研究了七个果蝇果蝇中多巴脱羧酶（Ddc）编码基因的核苷酸序列变异。在广泛采样的西班牙和罗利人口中，连锁不平衡的强度和模式有所不同。在西班牙人口中，少数几个地点具有很强的正相关性，而罗利人口中的许多地点却是非随机相关的，但相关性不强。连锁不平衡分析表明种群中存在两组单体型，每组均存在很大差异，表明存在上位性或倒位多态性。有证据表明自然选择作用于Ddc的两种形式。麦当劳·克雷特曼检验表明黑腹果蝇和模拟黑麦草之间的固定氨基酸差异不足，这可能是由于阴性选择。高频衍生的等位基因的过量，根据e--test检验是明显的，与搭便车的效果一致。搭便车的原因可能是所研究基因座的下游方向选择，如多态性与发散比逐渐降低所表明的。总之，Ddc基因座显然表现出复杂的变异模式，这是由于多种进化力所致。这种复杂的模式可能是功能上重要的基因密度异常高的结果。

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