Analysis of isoalleles and flanking SNPs of STR markers by NGS to distinguish monozygotic twins

Abstract

DNA analysis for forensic investigations is based on the concept that everyone is genetically unique, except in cases of monozygotic (MZ) twins. The most used markers are STRs, analyzed by CE, but they don’t allow the differentiation of MZ twins. Human identification using NGS is already part of some forensic laboratories and it enables reading the STRs’ sequence and its isoalleles, but there is no reference to this application for differentiation of MZ twins. Herein, we evaluated the possibility to distinguish MZ using the Precision ID GlobalFilerTM NGS STR Panel v2. The CE and NGS profiles were compared for 16 pairs of MZ, and the allele results were concordant, except for one pair, which showed an allele dropout on Penta D, probably because of its low coverage. We observed isoalleles in both individuals of 3 pairs, each in a different marker: D2S441, D12S391, and D4S2408, respectively, which did not allow the differentiation within each pair. However, we observed 2 flanking SNPs, each one in a pair, in only one individual of the pair: rs560609904 in TPOX (G016A) and rs569521603 in D6S1043 (G027B), highlighting the possibility of differentiating MZ twins.