Tamura Tomonori, Osawa Motoki, Kimura Ryosuke, Inaoka Yoshihiko, Tanaka Sachi, Satoh Fumiko, Sato Itaru
Scientific Crime Laboratory, Kanagawa Prefectural Police, Yamashitacho 155, Naka-ku, Yokohama 231-0023, Japan.
J Forensic Leg Med. 2013 Feb;20(2):112-6. doi: 10.1016/j.jflm.2012.05.005. Epub 2012 Jun 26.
To infer relatedness from genetic data based on short tandem repeats, the exact method, in which shared allele frequencies are applied to relevant equations, has been conventionally used. An alternative approach is the IBS method that is based on the number of shared alleles between individuals. In the present study, the performance of the IBS method in pairwise kinship analysis was compared with the exact method using simulated data of 10,000 genotype pairs for 15 loci in the ABI Identifiler system. The likelihood ratio in allele-sharing of zero, one and two was calculated from joint probabilities based on allele frequencies of the Japanese population. Whereas the IBS method generally produced lower values of combined indices, smaller deviations of the distributions were evident. The threshold for identification of full siblings relative to non-relatives was comparable with that of the exact method, indicating that both inference powers were almost identical. The likelihood ratio in the IBS method depends on the heterozygosity at a locus, and heterozygosities of the 15 loci were consistent across various population groups, particularly in East Asians. The convenience of fixed LR values in the IBS method is beneficial for cases with uncertain allele frequencies and rare alleles.
为了基于短串联重复从基因数据推断亲缘关系，传统上使用的是精确方法，即将共享等位基因频率应用于相关方程。另一种方法是基于个体间共享等位基因数量的IBS方法。在本研究中，使用ABI Identifiler系统中15个位点的10000对基因型模拟数据，将IBS方法在成对亲缘关系分析中的性能与精确方法进行了比较。根据日本人群的等位基因频率，从联合概率计算出等位基因共享为零、一和二时的似然比。虽然IBS方法通常产生较低的综合指数值，但分布的偏差较小。与非亲属相比，识别全同胞的阈值与精确方法相当，这表明两种推断能力几乎相同。IBS方法中的似然比取决于一个位点的杂合性，并且15个位点的杂合性在不同人群组中是一致的，特别是在东亚人群中。IBS方法中固定似然比值的便利性对于等位基因频率不确定和存在稀有等位基因的情况是有益的。
