Non-CODIS DNA markers could be more effective than CODISbased STRs in problematic biological relationship cases

Abstract

Short tandem repeat (STR) markers are used worldwide for forensic and paternity identification purposes. It has been proven that a commercial STR kit joined with supplemental STR loci will strengthen the power of resolving complex paternity cases. In the past years, we encountered two rare and difficult family relationship cases; CODIS-based commercial kits were initially used, but failed. We thus employed additional non-CODIS loci and finally resolved the cases. A total of 40 STRs, 13 CODIS and 27 non-CODIS, were profiled using an ABI 3130 Genetic Analyzer. In the two cases, the exclusionary events and percentage obtained from the non-CODIS markers were 9 (33%, out of 27 in case 1) and 18 (also 33%, out of 54 in case 2). Statistical results revealed that the non-CODIS STRs were significantly informative than the CODIS in identifying problematic kinship cases, and that the high case-resolving capability of the non-CODIS was irrelevant to repeat motif composition of STRs. Four index measures, heterozygosity rate, power of exclusion, power of discrimination, and polymorphism information content, were evaluated for the usefulness of both categories, also implying that the non-CODIS seemed to be more available than the CODIS. Our findings are in concordance with a previous research that the 13 core CODIS STRs are not sufficient to definitively differentiate between pairs of close relatives and may lead to false inclusions. The result, an indispensable system of the non-CODIS, could provide a reference for resolving similar complex relationship cases.

Forensic characteristics and population genetics of Chinese Kazakh ethnic minority with an efficient STR panel

“…It is worth noting that seven new markers were added up to these 13 core STR loci, creating an expanded panel with 20 CODIS core loci in 2015 (Hares, 2015). However, in forensic applications, it is indispensable to combine the non-CODIS STRs with the previously commercial CODIS STR kits in order to increase the discrimination power (Inokuchi et al, 2018; Kuzniar, Jastrzebska & Ploski, 2006; Tsai et al, 2013) in some cases, like missing person investigations, complicated parentage testing cases and those with mutation events. In this study, 22 selected loci (Li et al, 2017) were introduced containing 18 non-CODIS STR loci and four CODIS STR loci in which three (D1S1656, D2S1338 and D12S391) were recognized as CODIS core loci in 2015 (Hares, 2015) and one (D16S539) belonged to 13 CODIS core loci.…”