中文摘要：

在中国6个生活环境差异较大的少数民族群体中进行ATXN2基因编码区CAG重复的变异研究，以衡量其是否受到正选择的作用以及寻找推动选择作用的因素。采集6个民族群体共291个健康无关个体，对其进行STR分型，直接计数其等位基因及等位基因型频率，计算其线性Fst值，构建针对该基因的系统进化树，并对各群体进行MDS分析。线性风f值结果显示：回族和彝族群体间ATXN2基因STR位点进化的差异具有显著性，其他4个群体相互间无显著性差异。结合已报道的其他群体进一步分析，回族、哈尼族、云南蒙古族以及内蒙古自治区蒙古族每个人群都与日本人群有显著性差异；回族、内蒙古自治区蒙古族与汉族具有显著性差异。6个群体中ATXN2基因STR的等位基因频率有各自的分布特点，稀有等位基因频率变化产生的原因可能是选择作用的结果。

英文摘要：

Toinvestigate CAG repeats variation of ATXN2 gene coding region in six ethnic groups that live in compara- tively different environments, to evaluate whether these variations are under positive selection, and to find factors driving selection effects, 291 unrelated healthy individuals were collected from six ethnic groups and their STR geneotyping was performed. The frequencies of alleles and genotypes were counted and thereby Slatkin＇s linearized Fst values were calcu- lated. The UPGMA tree against this gene was constructed. The MDS analysis among these groups was carried out as well. The results from the linearized Fst values indicated that there were significant evolutionary differences of the STR in A TXN2 gene between Hui and ~i groups, but not among the other 4 groups. Further analysis was performed by combining our data with published data obtained from other groups. These results indicated that there were significant differences be- tween Japanese and other groups including Hui, Hani, Yunnan Mongolian, and Inner Mongolian. Both Hui and Mongolian from Inner Mongolia were significantly different from Han. In conclusion, the six ethnic groups had their own distribution characterizations of allelic frequencies ofATXN2 STR, and the potential cause of frequency changes in rare alleles could be the consequence of positive selection.