Description of Rare Genetic Variants Discovered with Promega PowerPlex® Forensic Amplification Kits during STR analysis of Routine Paternity and Kinship Cases

Abstract

Short Tandem Repeats (STR) have been widely used to create a discriminating DNA profile during the forensic investigation of a crime. The Paternity and Kinship Division at Medico-legal Directorate (MLD)/ Baghdad, provides a DNA fingerprinting service for paternity and kinship requests from different courts of law and police departments from across the country. Several rare variants were observed during DNA analysis such as rare off-ladder alleles, tri-allelic pattern as well as allele dropout. Variants that have been transmitted among family members were investigated in this study. During the period between 2008 to 2019, 38309 samples have been analyzed in the Paternity and Kinship Laboratories for DNA profiling to resolve the referred cases. DNA profiles found to have unusual STR patterns (off-ladder, tri-allelic pattern, inter-loci variable were analyzed and documented). A total of 17 variants were observed which were as shared among family members. Rare off-ladder alleles (9 cases + inter-loci variant 2 cases), as well as 6 cases of tri-allelic patterns were recorded. The presence of each type of these variants among family members proves that these variations are of genetic origin. They also represent rare genetic variants specific to the Iraqi populations that could be used for the establishment of a new Iraqi DNA database, which might be useful for genealogical studies as well as in terms of resolving familial, social, and moral disputes.