常染色体STR祖孙亲缘关系鉴定分析

Kinship Analysis of Grandparents and Grandchild with STR on Euchromosome

目的概括归纳一种简便易行的祖孙亲缘关系鉴定分析方法,对实际检案起到指导作用。方法根据孟德尔遗传规律、概率论和亲权指数(PI)值基本概念,归纳推导适用于常染色体STR各种基因型组合的祖孙亲缘关系似然率(LR)计算式及其代入参数。并应用于一个三代家系的祖孙鉴定及实际案例。结果祖孙亲缘似然率(LR)计算总共有三种计算式,它们概括了祖孙亲缘关系鉴定中的各种基因型遗传组合情形。公式中祖父母遗传可能的生父基因的概率可以简单地根据可能生父基因在祖父母基因型中所占的比例数来推定。祖孙亲缘关系鉴定分为孩子生母参与和不参与两种情况,同样的遗传指标检验分析后,前一种情形LRs明显升高,后一种情形LRs明显降低。结论用常染色体STR检验进行祖孙亲缘关系鉴定分析,在祖父、祖母均参与的情况下,其祖孙亲缘关系似然率的计算简单、直观、可操作性强;孩子生母尽可能参与检验,否则需要增加检验STR位点的数量才能获得更加明确的结论。

Objective To generalize a easy likelihood ratio（LR） numeration for kinship analysis of grandparents and grandchild when the alleged father or mother＇s genotype were not available. Methods Based on the principle of genetics, definition of paternity index and theory of probability, three expressions for kinship analysis of grandparents and grandchild were induced, and with which the LRs of STR loci in both a real pedigree of five members and a civil case were calculated and analyzed. Results The induced three expressions were suitable for the LRs calculation of all kinds of genotype permutation and combination of grandparents and grandchild. In addition, the involved probability of obliged gene at each STIR locus inherited from grandparents could be simply derived from the percentage of the obliged gene in grandparents four alleles. It was shown that the LRs calculated in motherless cases is much smaller than that in mother-involved cases. Conclusion The method was quite suitable for calculation of LRs between grandparents and grandchild. In motherless cases, it is suggested that more STR locus should be analyzed.