Short tandem repeat (STR) typing has been regularly used in paternity disputes and forensic human identification linked caseworks. Occasionally, forensic scientists come across aberrant allele patterns during STR typing because of mutations, genetic variations, and other abnormalities. The tri-allelic pattern of STR is rare, particularly, the case where this pattern exists at 4 loci. Here, we report the type II tri-allelic patterns observed at vWA, SE33, D8S1179, and D13S317 loci in the product of conception (POC) sample during the course of our regular paternity case investigation. The DNA extracted from the blood samples and tissue of POC were subjected to STR typing for autosomal and sex STR loci using the commercial QIAGEN’s Investigator^® IDplex Plus Kit and QIAGEN’s Investigator^® 24plex QS Kit. Capillary electrophoresis was carried out in 3500 and 3500xL Genetic Analyzer Applied Biosystems and genotyped using GeneMapper ID-X Software v1.5 and v1.6. In this case of paternity inclusion, the POC sample displayed type II tri-allelic patterns at vWA (16, 19, 20), SE33 (19, 28.2, 29.2), D13S317 (16, 19, 20), and D8S1179 (10, 13, 17) loci. In addition, the POC displayed an abnormal genotype with a heterozygous peak imbalance (type II-B) of (1:2) pattern at D3S1358, D21S11, and D16S539 loci, of (2:1) pattern at D1S1656, D12S391, D10S1248, D2S1338, D2S441, D18S317, FGA, CSF1PO, and D5S818 loci, and type II-C allelic pattern (one single peak with triplicate height) at D19S433 and DS7820 loci. Understanding of such anomalous genotypes improves the knowledge about tri-allelic pattern of CODIS loci and helps in the appropriate interpretation of the results in STR typing.

短串联重复 (STR) 分型经常用于亲子纠纷和法医人类身份识别相关案件。有时，法医科学家在 STR 分型过程中会发现由于突变、遗传变异和其他异常而导致的异常等位基因模式。 STR 的三等位基因模式很少见，特别是该模式存在于 4 个基因座的情况。在这里，我们报告了在常规亲子鉴定案例调查过程中在受孕产物 (POC) 样本中观察到的 vWA、SE33、D8S1179 和 D13S317 位点的 II 型三等位基因模式。使用商业 QIAGEN 的 Investigator ^® IDplex Plus 试剂盒和 QIAGEN 的 Investigator ^® 24plex QS 试剂盒对从 POC 的血液样本和组织中提取的 DNA 进行常染色体和性别 STR 位点的 STR 分型。在 3500 和 3500xL 遗传分析仪 Applied Biosystems 中进行毛细管电泳，并使用 GeneMapper ID-X 软件 v1.5 和 v1.6 进行基因分型。在这种亲子包含的情况下，POC 样本在 vWA (16, 19, 20)、SE33 (19, 28.2, 29.2)、D13S317 (16, 19, 20) 和 D8S1179 (10, 13, 17) 基因座。此外，POC 显示异常基因型，在 D3S1358、D21S11 和 D16S539 基因座上具有 (1:2) 模式的杂合峰不平衡（II-B 型），在 D1S1656、D12S391、D10S1248 上具有 (2:1) 模式， D2S1338、D2S441、D18S317、FGA、CSF1PO 和 D5S818 基因座，以及 D19S433 和 DS7820 基因座处的 II-C 型等位基因模式（一个具有三重重复高度的单峰）。了解此类异常基因型可以提高对 CODIS 位点三等位基因模式的了解，并有助于正确解释 STR 分型结果。