母胎混合STR分型流产胎儿的亲权指数计算方法探讨  

Discussion on parentage index calculation of aborted fetuses with mixed STR typing

作　　者：余华光 曹禹[1] 黄江平[1] 孟必成 郝思静 江华 杨帆[1] Yu Huaguang;Cao Yu;Huang Jiangping;Meng Bicheng;Hao Sijing;Jiang Hua;Yang Fan(Key Laboratory of Forensic Genetic Techniques for Crime Scenes,Ministry of Public Security,Institute of Forensic Science,Shanghai Municipal Public Security Bureau,Shanghai 200083)

机构地区：[1]法医物证学现场应用技术公安部重点实验室,上海市公安局物证鉴定中心,上海200083

出　　处：《中国法医学杂志》2024年第5期530-534,共5页Chinese Journal of Forensic Medicine

基　　金：上海市科学技术委员会科研计划项目(21JG0500200)。

摘　　要：目的 在流产胎儿获得母胎混合STR分型的案、事件中,对疑似生父进行亲权指数计算提出两种计算方法,为包含混合分型的亲权鉴定提供理论参考。方法 依据是否先拆分出胎儿基因型,提出拆分胎儿基因型亲权指数计算法和推断生父基因亲权指数计算法。结果 拆分胎儿基因型亲权指数计算法,是先将胎儿基因型拆分出来,再按照标准三联体进行亲权指数计算。推断生父基因亲权指数计算法,是不考虑混合分型中峰高、峰面积的比例,推断出所有符合孟德尔遗传定律的生父基因(推断),再分别计算亲权指数,取其中的最小值作为该基因座的亲权指数。结论 当流产组织混合分型中,胎儿混合比率M_(R)≥0.43时,拆分准确性极高,使用拆分胎儿基因型亲权指数计算法计算结果准确性也极高,建议使用拆分胎儿基因型亲权指数计算法。当0.05≤M_(R)<0.43时,建议使用推断生父基因亲权指数计算法,可以最大程度的避免对无关人员的误判。当M_(R)<0.05时,胎儿等位基因丢失的潜在风险极高,不建议对混合斑进行亲权鉴定。由于推断生父基因亲权指数计算法得出的累计亲权指数通常低于拆分胎儿基因型亲权指数计算法,在检出的基因座较少的情况下,可能出现累计亲权指数低于10 000的情况,此时应增加检测遗传标记。Objective In cases and events of mixed STR typing of aborted fetus,two methods for calculating paternity index(PI)of suspected biological fathers are proposed,which could be useful for theoretical reference for parental identification including mixed STR typing.Methods Depending on whether the fetal genotypes can be identified,the simple PI calculation method and the PI calculation method of deduced biological paternal genes when the fetal genotypes cannot be identified are proposed.Results The simple PI calculation method is to indentify the fetal genotypes first and then calculate according to the standard triplet.The PI calculation method of deduced biological paternal genes is to deduce all the possible genotypes of biological fathers conforming to Mendel’s law(inference)without considering the ratio of peak height and peak area in mixed typing,and then calculate the parental index separately,taking the minimum value as the parental index of the locus.Conclusion When mixture ratio of fetus in the mixed typing of aborted tissue M_(R)≥0.43,the accuracy of separation is very high and the simple PI calculation method can be accurate,so it is recommended.If 0.05≤M_(R)<0.43,it is suggested to use the calculation method of deduced biological paternal genes,which can avoid misjudgment of irrelevant persons to the greatest extent.If M_(R)<0.05,there's a high risk of fetal allele loss,we should not perform a paternity test on the mixed spot.Since the cumulative parental index calculated by deduced the biological paternal genes is usually lower than the value calculated by dividing the fetal genotype,the CPI may be lower than 10000 when fewer loci are identified,and then more genetic markers should be detected.

关 键 词：法医遗传学 短串联重复序列 混合分型 亲权指数 混合比率 

分 类 号：D919.2[医药卫生—法医学]