常染色体STR基因座母源突变的观察分析与亲权指数计算

Analysis of maternal mutations of autosomal STR loci and paternity index calculation

目的 观察20个常染色体STR基因座在广东省汉族人群中发生母源突变的情况,分析母源突变基因座的亲权指数计算方法并探讨在亲子鉴定实践中的应对策略。方法 利用10 271例家系样本,提取基因组DNA,采用PowerPlex;21试剂盒扩增20个常染色体STR基因座,PCR扩增产物经过毛细管电泳后分析STR基因座的等位基因分型,观察母源突变的突变率、突变基因座等位基因片段大小及核心重复单位的增减情况等特点,分析突变STR基因座的亲权指数计算方法。结果 除TH01基因座和D7S820基因座外,在18个STR基因座共观察到86例母源突变现象,突变率在0.003%~0.05%之间。核心重复序列增加的占51.2%,减少的占32.6%。突变发生在中等长度等位基因的占87.2%。结论 STR基因座的母源突变发生率较低。主要为一步突变,核心重复序列增加情况较多。突变主要发生在基因座的中等长度等位基因。发生母源突变的单亲鉴定,建议增加STR检测位点。

Objective To observe the maternal mutations of 20 autosomal STR loci in Guangdong Han population, analyze paternity index calculation methods in maternal mutation loci and explore the strategies in the practice of paternity test. Methods Genomic DNA was extracted from samples of 10271 families and PowerPlex;21 kit was used to amplify 20 autosomal STR loci. The allele types of STR loci were analyzed after capillary electrophoresis of the PCR products. We observed the characteristics of mutation rate, allele size of mutation STR locus and the change of repeat units. We also analyzed the calculation method of paternity index for mutant STR loci. Results Except for TH01 and D7 S820 loci, we observed 92 maternal mutations at 18 STR loci. The mutation rates were 0.0033%-0.05%. The increase of core repetitive sequence was 51.2% and the decrease of core repetitive sequence was 32.6%. The mutations occurred in the mid-length alleles accounting for 87.2%. Conclusion The maternal mutation rate of STR locus was low. It was mainly one-step mutation, and the increase of core repetitive sequence accounted for more. Mutations occurred mainly at the mid-length alleles of the locus. Additional STR loci were recommended for duo paternity test with maternal mutation.