Jobling M A, Williams G A, Schiebel G A, Pandya G A, McElreavey G A, Salas G A, Rappold G A, Affara N A, Tyler-Smith C
Department of Genetics, University of Leicester, University Road, Leicester LE1 7RH, UK.
Curr Biol. 1998;8(25):1391-4. doi: 10.1016/s0960-9822(98)00020-7.
DNA analysis is making a valuable contribution to the understanding of human evolution [1]. Much attention has focused on mitochondrial DNA (mtDNA) [2] and the Y chromosome [3] [4], both of which escape recombination and so provide information on maternal and paternal lineages, respectively. It is often assumed that the polymorphisms observed at loci on mtDNA and the Y chromosome are selectively neutral and, therefore, that existing patterns of molecular variation can be used to deduce the histories of populations in terms of drift, population movements, and cultural practices. The coalescence of the molecular phylogenies of mtDNA and the Y chromosome to recent common ancestors in Africa [5] [6], for example, has been taken to reflect a recent origin of modern human populations in Africa. An alternative explanation, though, could be the recent selective spread of mtDNA and Y chromosome haplotypes from Africa in a population with a more complex history [7]. It is therefore important to establish whether there are selective differences between classes (haplotypes) of mtDNA and Y chromosomes and, if so, whether these differences could have been sufficient to influence the distributions of haplotypes in existing populations. A precedent for this hypothesis has been established for mtDNA in that one mtDNA background increases susceptibility to Leber hereditary optic neuropathy [8]. Although studies of nucleotide diversity in global samples of Y chromosomes have suggested an absence of recent selective sweeps or bottlenecks [9], selection may, in principle, be very important for the Y chromosome because it carries several loci affecting male fertility [10] [11] and as many as 5% of males are infertile [11] [12]. Here, we show that one class of infertile males, PRKX/PRKY translocation XX males, arises predominantly on a particular Y haplotypic background. Selection is, therefore, acting on Y haplotype distributions in the population.
DNA分析为人类进化的理解做出了重要贡献[1]。许多注意力都集中在线粒体DNA（mtDNA）[2]和Y染色体[3][4]上，这两者都不会发生重组，因此分别提供了母系和父系谱系的信息。人们通常认为，在mtDNA和Y染色体位点上观察到的多态性是选择性中性的，因此，现有的分子变异模式可以用来推断种群在漂变、种群迁移和文化习俗方面的历史。例如，mtDNA和Y染色体的分子系统发育汇聚到非洲最近的共同祖先[5][6]，这被认为反映了现代人类种群在非洲的近期起源。然而，另一种解释可能是，mtDNA和Y染色体单倍型最近从非洲在一个历史更为复杂的种群中选择性传播[7]。因此，确定mtDNA和Y染色体的类别（单倍型）之间是否存在选择性差异，如果存在，这些差异是否足以影响现有种群中单倍型的分布就很重要。对于mtDNA，这一假设已有先例，即一种mtDNA背景会增加患Leber遗传性视神经病变的易感性[8]。尽管对全球Y染色体样本的核苷酸多样性研究表明近期不存在选择性清除或瓶颈效应[9]，但原则上，选择对Y染色体可能非常重要，因为它携带多个影响男性生育力的位点[10][11]，并且多达5%的男性不育[11][12]。在这里，我们表明，一类不育男性，即PRKX/PRKY易位XX男性，主要出现在特定的Y单倍型背景上。因此，选择作用于种群中的Y单倍型分布。
