Markow T, Hedrick P W, Zuerlein K, Danilovs J, Martin J, Vyvial T, Armstrong C
Department of Zoology, Arizona State University, Tempe 85287-1501.
Am J Hum Genet. 1993 Oct;53(4):943-52.
The characterization and analysis of genetic variation at the HLA loci provides important insight for population geneticists trying to understand the evolutionary forces that have shaped human populations. This study describes the HLA-A and HLA-B loci serotyping and statistical analysis on an isolated Native American population, the Havasupai of Arizona. Four alleles at the HLA-A locus were identified, while eight alleles were found at the HLA-B locus. These variants were present as 20 of 32 potential two-locus haplotypes, with five of the six most common haplotypes exhibiting high positive linkage disequilibrium. Significant homozygote deficiency (heterozygosity excess) was detected both at HLA-A and at HLA-B. This deviation from Hardy-Weinberg proportions was not attributable to nonselective causes such as different allele frequencies in males and females or avoidance of consanguineous matings. In addition, the distribution of alleles at both HLA-A and HLA-B was more even than expected from neutrality theory; that is, the observed Hardy-Weinberg homozygosity was only 62.4% of that expected under neutrality. These observations suggest that balancing selection is of major importance in maintaining genetic variation at HLA-A and HLA-B.
对HLA基因座的遗传变异进行特征描述和分析，可为试图了解塑造人类群体的进化力量的群体遗传学家提供重要见解。本研究描述了对一个孤立的美洲原住民群体——亚利桑那州的哈瓦苏派人——的HLA - A和HLA - B基因座进行血清分型及统计分析的情况。在HLA - A基因座鉴定出4个等位基因，而在HLA - B基因座发现了8个等位基因。这些变异以32种潜在的两位点单倍型中的20种形式存在，6种最常见的单倍型中有5种表现出高度正连锁不平衡。在HLA - A和HLA - B基因座均检测到显著的纯合子缺乏（杂合子过剩）。这种偏离哈迪 - 温伯格比例的情况并非归因于非选择性原因，如男性和女性不同的等位基因频率或近亲交配的避免。此外，HLA - A和HLA - B基因座的等位基因分布比中性理论预期的更为均匀；也就是说，观察到的哈迪 - 温伯格纯合度仅为中性条件下预期值的62.4%。这些观察结果表明，平衡选择在维持HLA - A和HLA - B基因座的遗传变异方面具有重要作用。
