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目的 了解中国 4个人群中 MICA基因第 5外显子 (GCT) n位点的遗传多态性并从遗传学的角度提供白马藏族起源的初步证据。方法 411个无血缘关系个体的血标本或唾液标本分别采自四川平武县白马藏族、西藏拉萨和云南中甸县藏族、成都地区汉族以及四川茂县羌族。以 1对跨越 MICA基因第 5外显子 GCT重复序列区的引物扩增基因组 DNA,产物用变性聚丙烯酰胺凝胶电泳分离 ,银染显色分析。结果 在 4个群体中均检测出 5种已报道的等位片段 ,并均以 A5最常见 ,在白马藏族、藏族、成都汉族和羌族中的频率分别为 0 .32 5、0 .345、0 .390和 0 .319。 A5 .1在成都汉族和羌族中占第 2位 ,频率分别为0 .2 30和 0 .2 93,A4和 A9在白马藏族和藏族中分别占第 2位 ,频率分别为 0 .2 5 4和 0 .2 72。上述各等位基因分布在 4个群体中存在差异 ,尤其是白马藏族与其它 3个群体之间存在显著差异。结论 MICA基因在迄今已研究的不同群体中都有 5种等位基因 ,提示 MICA基因在各群体间是在相似选择压力下产生 ,对维持群体的生理功能有着必不可少的作用。各民族 MICA等位基因的分布支持白马藏族可能是一个不同于藏族而相对独立起源的人群
Objective To understand the genetic polymorphisms at the n-site of exon 5 (GCT) of MICA gene in four Chinese populations and to provide preliminary evidence of the origin of white-horse Tibetan from the perspective of genetics. Methods Blood samples or saliva samples from 411 unrelated individuals were collected from Baima Tibetan in Pingwu County, Sichuan Province, Tibetans in Lhasa, Tibet and Zhongdian County in Yunnan Province, Han nationality in Chengdu Region, and Qiang Ethnic Group in Maoxian County, Sichuan Province. Genomic DNA was amplified using a pair of primers that spanned the GCT repeat region of exon 5 of MICA gene. The products were separated by denaturing polyacrylamide gel electrophoresis and analyzed by silver stain. Results Five reported allelic fragments were detected in all four populations, most of which were detected by A5 gene. The frequencies of alleles in Baima Tibetan, Tibetan, Chengdu Han and Qiang were 0 .32 5,0 .345,0 .390 and 0 .319. A5.1 ranked the second place among the Han and Qiang ethnic groups in Chengdu at a frequency of 0.230 and 0.22, respectively, while A4 and A9 ranked second in the Baima Tibetan and Tibetan nationalities with a frequency of 0.244 And 0 .2 72. The distribution of the above alleles is different among the four groups, in particular, there are significant differences between the White Horse and other three groups. Conclusion The MICA gene has five alleles in different groups studied so far, suggesting that the MICA gene is produced under similar selection pressure among different groups and plays an indispensable role in maintaining the physiological function of the population. Distribution of ethnic MICA alleles Supports the White Horse Tibetan may be a relatively independent of Tibetan origin and population