20723例亲子鉴定中19个STR基因座的突变分析

目的观察并分析肯定亲权关系的案件,探索STR基因座的突变规律。方法采用Goldeneye 20A试剂盒对20723例肯定亲权关系的案件筛选等位基因突变事件,统计各基因座的突变率和突变等位基因的来源、片段大小、突变步数及重复单位的增加或减少情况,分析突变相关因素的特点。结果 19个STR基因座共发现548例突变,观察到557个突变事件,基因座的突变率为0.07‰~2.23‰。父系突变与母系突变的比例为3.06∶1。突变以一步突变为主,增加与减少重复单位的情况相当;二步以上(含二步)突变更易出现重复单位减少。突变主要发生于中等位基因,重复单位增减比例相当,长等位基因突变中重复单位减少显著多于增加。父系突变出现重复单位增加与减少的比例相当,母系突变重复单位减少较增加多见。结论各基因座的突变率差异具有统计学意义,当出现1~2个基因座不符合遗传规律时,应当加测其他检测系统,并结合突变基因座的信息计算PI值,以进一步明确鉴定意见。

Mutation Analysis of 19 STR Loci in 20723 Cases of Paternity Testing

Objective T o observe and analyze the confirm ed cases of paternity testing, and to explore the m utation rules of ST R loci. Methods T he m utant ST R loci w ere screened from 20723 confirm ed cases of paternity testing by G oldeneye 20A system .T he m utation rates, and the sources, fragm ent length, steps and increased or decreased repeat sequences of m utant alleles w ere counted for the analysis of the characteristics of m utation-related factors. Results A total of 548 m utations w ere found on 19 ST R loci, and 557 m utation events w ere observed. T he loci m utation rate w as 0.07‰-2.23‰. T he ratio of pater-nal to m aternal m utant events w as 3.06:1. O ne step m utation w as the m ain m utation, and the num ber of the increased repeat sequences w as alm ost the sam e as the decreased repeat sequences. T he repeat se-quences w ere m ore likely to decrease in tw o steps m utation and above. M utation m ainly occurred in the m edium allele, and the num ber of the increased repeat sequences w as alm ost the sam e as the decreased repeat sequences. In long allele m utations, the decreased repeat sequences w ere significantly m ore than the increased repeat sequences. T he num ber of the increased repeat sequences w as alm ost the sam e as the decreased repeat sequences in paternal m utation, w hile the decreased repeat sequences w ere m ore than the increased in m aternal m utation. Conclusion T here are significant differences in the m utation rate of each locus. W hen one or tw o loci do not conform to the genetic law , other detection system should be added, and PI value should be calculated com bined w ith the inform ation of the m utate ST R loci in order to further clarify the identification opinions.