Genotyping irregularities observed in STR markers used in forensics and human identification in the Lebanese population

Forensic DNA analysis is based on the evaluation of DNA profiles obtained from reference samples or crime scene traces. Profiles are determined using different commercial STR multiplex kits, which includeallelic ladders for the correct designation of alleles ofa given STR system. However, some new STR variants could be observed and their identification is essential for proper allele size calling in casework interpretation and cases of kinship matching or relationship testing. A total of 6392 samples were analyzedas part of the DNA work at our DNA testing facility from 2004 until 2016, where one hundred and twelvenew different STR variant alleles of 20STR loci wereobserved in the Lebanese population. Forty-fiveof these variant alleles were internationally reported in the STR-base whereas the remainingsixty-sevenalleles were observed for the first time. The loci included D3S1358, D19S433, D21S11, D13S317, TPOX, FGA, D7S820, D18S51, CSF1PO, D2S1338, D10S1248, D12S391, D22S1045, D2S441, Penta-D, Penta-E, SE33, D1S1656, vWA, and THO1.Also, four triallelic patterns were observed at D21S11, D12S391, D13S317 and Penta-D loci. Primer binding site mismatch that resulted in a discordance between the amplification of different kits was observed once attheD19S433 locus.