Genotyping irregularities observed in STR markers used in forensic DNA analysis in the Lebanese population

Abstract EN

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 include allelic ladders for the correct designation of alleles of a 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 analyzed as part of the DNA work at our DNA testing facility from 2004 until 2016, where one hundred and twelve new different STR variant alleles of 20 STR loci were observed in the Lebanese population.

Forty-five of these variant alleles were internationally reported in the STR-base whereas the remaining sixty-seven alleles 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 at the D19S433 locus.