全同胞与半同胞关系甄别中似然比的算法  

Algorithms of Likelihood Ratio for Discriminating Full Sibling from Half Sibling

作　　者：赵书民[1] 张琳娜[2] 张素华[1] 张娜[1] 赵珍敏[1] 李成涛[1] 

机构地区：[1]司法部司法鉴定科学技术研究所 上海市法医学重点实验室,上海200063 [2]北京市第九中学生物教研组,北京100041

出　　处：《法医学杂志》2012年第2期104-108,共5页Journal of Forensic Medicine

基　　金：国家"十二五"科技支撑项目(2012BAK16B01);中央级科研院所公益研究项目(GY1103);上海市法医学重点实验室资助项目(11DZ2271500)

摘　　要：目的推导单亲参与及双亲皆无情形下甄别全同胞与半同胞关系时似然比的计算公式。方法分别建立单亲参与和双亲皆无情形下进行全同胞与半同胞关系甄别的检验假设,依据贝叶斯原理计算原假设与备择假设对应的遗传学证据的条件概率,并对备择假设与原假设条件下的遗传学证据的条件概率比值进行化简。通过实际案例对推导得到的似然比计算公式进行验证。结果若有单亲参与,两名孩子在同一基因座共有14种不同的基因型组合,对应的似然比计算公式有5种;若双亲皆无,则共有11种不同的基因型组合,对应的似然比计算公式有7种。单亲参与时,所建立的似然比算法的把握度要高于全同胞指数与半同胞指数比值法。结论获得的不同情形下甄别全同胞与半同胞的似然比计算公式对于相关案例的鉴定具有实际应用价值。Objective To derive the formulae for likelihood ratio calculation in discriminating full sibling from half sibling with single-parent participation or without parent participation.Methods Null hypothesis and alternative hypothesis were established for discriminating full sibling from half sibling in two circumstances： two children with single-parent and without parent participation.Conditional probabilities of the genetic evidentiary under null and alternative hypotheses were calculated according to the Bayesian theory.The likelihood ratios were established with the conditional probability under alternative hypothesis division that under null hypothesis,followed with simplification.All the formulae were validated in a real case.Results While mother or fathers＇ genetic information available in differentiating full sibling from half sibling,14 different genotype combinations could be shared by the two detected children at a given locus and the likelihood ratio could be calculated with 5 different formulae respectively.While both parents＇ genetic information unavailable,11 different genotype combinations could be shared and the likelihood ratio could be calculated with 7 different formulae respectively.It was validated in a real case that the power of the likelihood ratio method developed for discriminating full sibling from half sibling with single-parent participation was higher than that of the ratio of full sibling index over half sibling index.Conclusion The formulae of likelihood ratio developed are useful for discriminating full sibling from half sibling with single-parent participation or without parent participation.

关 键 词：法医遗传学 同胞关系 似然比 

分 类 号：R714.254[医药卫生—妇产科学]