三种类型突变情形下祖孙关系指数的计算方法  

Calculating Methods of Grandparent Index in the Presence of Mutation under Three Conditions

作　　者：章俊 周密 高升杰 ZHANG Jun;ZHOU Mi;GAO Shengjie(Anhui Baiyou Judicial Identifi cation Center,Hefei 230081,China;Wuhu Public Security Bureau,Wuhu 241000,Anhui,China;Forensic Genomics International(FGI),Shenzhen 518083,Guangdong,China)

机构地区：[1]安徽百友司法鉴定中心,合肥230081 [2]芜湖市公安局,安徽芜湖241000 [3]深圳华大法医科技有限公司,广东深圳518083

出　　处：《刑事技术》2025年第1期68-73,共6页Forensic Science and Technology

摘　　要：祖孙鉴定是亲子鉴定中的一项重要内容,包括双祖亲母鉴定、双祖疑母鉴定和双祖鉴定3类。目前,关于祖孙鉴定的祖孙关系指数(GI),在突变情形下未见成体系的公式报道。本研究首先建立祖父×祖母基因型简化表述模型,并推导亲代的等位基因突变为子代等位基因的通用概率公式(P(DG→Z))。其次在P(DG→Z)公式基础上,分别推导双祖亲母GI(GIDGBM)、双祖疑母GI(GIDGAM)和双祖GI(GIDG)的通用公式。根据祖父母、母亲和孩子的基因型,三种类型的GI公式均进一步细化为分项公式。设计模拟实验在EX30试剂盒的30个常染色体基因座上统计无关个体组中5种遗传类型的百分比。最后分别建立模拟亲缘组和无关个体组模型,统计CGI的几何平均数(Π)、95%置信区间(CI)、亲缘组中CGI<10 000的百分比和无关个体组中CGI>0.000 1的百分比。本研究推导出突变情形下3种祖孙鉴定类型的全部GI公式,任意分型组合均可计算对应的GI。在EX30系统中,双祖疑母鉴定的所有亲缘组和无关个体组均可获得明确结论;双祖亲母鉴定中所有亲缘组和99.89%的无关个体组可获得明确结论;双祖鉴定中两组均需要增加检测更多遗传标记。本研究结果表明,本文公式可应用于突变情形下3种祖孙鉴定类型的GI计算。Kinship analysis of grandparents and grandchildren is an important content in thefield of forensic identification,which includes three subtypes:double grandparents and biological mother test(DGBM),double grandparents and alleged mother test(DGAM),and double grandparents test(DG).Until now,no systematic formula has been reported in grandparent index(GI)calculation of grandparent identification in the presence of mutation,apart from few simple calculation methods of partial gene combination in DGBM.In this study,wefirst created a simplified representation model of grandfather and grandmother in 5 subtypes,in the form of a set of genotypes.The general probability formula of mutation of parent genotype into child genotype(P(DG→Z))was derived in 12 subtypes.Furthermore,the general formulas of GI under three conditions were derived:GI of double grandparents and biological mother(GIDGBM),GI of double grandparents and alleged mother(GIDGAM)and GI of double grandparents(GIDG).The detailed formulas were further refined according to genotypes of double grandparents,mother and grandchild.In addition,the percentages of mutations of 5 genetic types in the group of unrelated individuals on 30 STR loci of the EX30 kit were calculated.Finally,models of simulated kinship groups and unrelated individual groups were established respectively.The geometric mean(Π)and 95%confidence interval(CI)of CGI,the percentages of cases where CGI<10000 in kinship groups,and the percentages of cases where CGI>0.0001 in unrelated individual groups were calculated in the same 30 STR loci.In this study,the novel formulas can be used to calculate all kinds of GI in the presence of mutation under three conditions.The genotype combinations in all mutation cases were reviewed.Among them,the occurrence rate of both paternal and maternal mutation groups was 13.31%,which could not be ignored.In EX30 kit,the formulas can achievefirm conclusions in DGAM cases for both the kinship group and unrelated individual group;in DGBM cases identifications,all cases i

关 键 词：法医遗传学 常染色体STR 祖孙关系鉴定 祖孙关系指数 突变 

分 类 号：DF795.2[医药卫生—法医学]