IBD法在堂表亲缘关系鉴定中的应用

目的使用血缘一致性(identity by descent,IBD)法计算堂表亲缘关系的堂表关系指数(first cousin index,FCI)和累积堂表关系指数(combined first cousin index,CFCI),为IBD法鉴定两个个体是否具有堂表亲缘关系提供科学手段。方法取124对堂表兄弟姐妹和186对无亲缘关系个体的口腔拭子,检验每人18个常染色体STR基因座的等位基因,用IBD法计算堂表对和无关个体对的FCI和CFCI,并用判别分析的方法对两组样本的FCI和CFCI计算结果进行分析。结果 CFCI在堂表对和无关个体对中的频率分布呈偏正态分布,前者的平均值和标准差为11.864和21.678,后者为0.605和0.988,两者具有显著差异。以CFCI/(CFCI+1)≥0.6为标准,堂表对和无关个体对判别准确率为88.387%;依据各常STR基因座的FCI计算结果建立判别方程,多元判别方程和多元逐步判别方程的判别准确率分别为92.258%和91.935%。结论用IBD法和依据IBD建立的判别分析法可以用于堂表亲缘关系的筛选。

Application of IBD method in cousinship identification

Objective Identity by descent(IBD) method is used to calculate the first cousin index(FCI) and the combined first cousin index(CFCI) of the cousins, so as to provide a scientific method for identifying whether two individuals have the cousinship by the IBD method. Methods Oral swabs from 124 pairs of cousins and 186 pairs of unrelated individuals were taken to examine the alleles of 18 autosomal STR loci. The FCI and the CFCI of cousin pairs and unrelated individual pairs were calculated by IBD method, and the FCI and the CFCI results of the two groups were analyzed by discriminant analysis. Results The CFCI in cousin pairs and unrelated pairs showed a skew normal distribution. The average and standard deviation of the former were 11.864 and 21.678, while those of the latter were 0.605 and 0.988. There was significant difference between the two groups. Taking CFCI/(CFCI+1) ≥ 0.6 as the standard, the discrimination accuracy of cousin pairs and unrelated individuals is 88.387%. The discriminant equation was established according to the IBD calculation results of each STR locus. The results showed that the discriminant accuracy of multivariate discriminant equation and multivariate stepwise discriminant equation were 92.258% and 91.935%, respectively. Conclusion The IBD method and the discriminant analysis based on IBD method can be used to screen the genetic relationship of the cousins.