Objectives: To investigate the efficacy of different numbers of microhaplotype (MH) loci and the introduction of different reference samples on the identification of full sibling, half sibling and differentiation between full sibling and half sibling kinships, and to explore the effect of changing mutation rate on sibling testing.
Methods: First, a family map involving three generations was established, and four full sibling identification models, five half sibling identification models and five models distinguishing full and half siblings were constructed for different reference samples introduced. Based on the results of the previous study, two sets of nonbinary SNP-MH containing 34 and 54 loci were selected. Based on the above MH loci, 100 000 pairs of full sibling vs. unrelated individuals, 100 000 pairs of half sibling vs. unrelated individuals and 100 000 pairs of full sibling vs. half sibling were simulated based on the corresponding sibling kinship testing models, and the efficacy of each sibling kinship testing model was analyzed by the likelihood ratio algorithm under different thresholds. The mutant rate of 54 MH loci was changed to analyze the effect of mutation rate on sibling identification.
Results: In the same relationship testing model, the systematic efficacy of sibling testing was positively correlated with the number of MH loci detected. With the same number of MH loci, the efficacy of full sibling testing was better than that of uncle or grandfather when the reference sample introduced was a full sibling of A, but there was no significant difference in the identification efficacy of the four reference samples introduced for full sibling and half sibling differentiation testing. In addition, the mutation rate had a slight effect on the efficacy of sibling kinship testing.
Conclusions: Increasing the number of MH loci and introducing reference samples of known relatives can increase the efficacy of full sibling testing, half sibling testing, and differentiation between full and half sibling kinships. The level of mutation rate in sibling testing by likelihood ratio method has a slight but insignificant effect on the efficacy.
目的: 探究不同数量微单倍型（microhaplotype，MH）位点和引入不同参考样本对全同胞、半同胞关系鉴定及区分全和半同胞关系鉴定的效能影响，并探讨改变突变率对于同胞关系鉴定的影响。方法: 首先建立一个涉及三代人的家庭图谱，针对引入的不同参考样本构建4种全同胞关系鉴定模型、5种半同胞关系鉴定模型和5种区分全和半同胞关系模型。基于前期研究结果筛选出分别包含34和54个位点的两组非二等位SNP-MH，基于上述MH位点在相应的同胞关系鉴定模型下，模拟100 000对全同胞-无关个体、100 000对半同胞-无关个体和100 000对全同胞-半同胞，并利用似然比法分析每种同胞关系鉴定模型在不同阈值下的效能，改变54个MH位点的突变率，分析突变率对于同胞关系鉴定的影响。结果: 在同一种关系鉴定模型中，同胞关系鉴定的系统效能与检测的MH位点数量呈正相关。在相同MH位点数量下，引入的参考样本为A的全同胞时，全同胞关系鉴定的效能优于引入A的叔叔或祖父，但对于半同胞关系鉴定和区分全和半同胞关系引入的4种参考样本对于鉴定效能的增加没有显著差异。此外，突变率的高低对同胞关系鉴定效能略有影响。结论: 增加检测MH位点的数量和引入已知亲属参考样本均能够增加全同胞关系鉴定、半同胞关系鉴定、区分全和半同胞关系的效能。以似然比法进行同胞关系鉴定时突变率的高低对效能产生轻微影响，但不显著。.
Keywords: autosomes; forensic genetics; full sibling; half sibling; likelihood ratio method; microhaplotype; reference sample; sibling.