Relationship testing through DNA profiling may undesirably be affected by the rare allele variants, tri-allelic patterns and null alleles. Therefore, it is vital to report such anomalies. We report a paternity testing instance in a sexual assault case studied at Punjab Forensic Science Agency (PFSA), Lahore, Pakistan showing a unique allele variant in mother and child.
DNA was extracted from the buccal swabs of reference samples using organic extraction method. DNA profiling was done for 15 autosomal STRs and amelogenin using Identifiler Plus kit.
A novel out of marker range (OMR) allele variant between STR Loci D16S539 and D2S1338 was observed in the DNA profiles of victim and her child. At STR locus D2S1338, twenty-one different allele variants are listed at STRBase ranging from 11 to 28. The allele variant observed in this case study appeared at less than the marker range (< D2S1338) with a size of 297.50 bp. The novel variant OMR allele at D2S1338 was calculated as allele 13 with the help of allelic ladder. Moreover, this allele variant (allele 13 at locus D2S1338) was present in only two other distinct DNA profiles in PFSA DNA database, out of a total 10,125 profiles.
The overall frequency of this unique allele variant was 3 in 10,125 unrelated individuals with occurrence frequency of 0.000296. According to our limited knowledge, it is the first report of a novel OMR allele variant at D2S1338 within the Pakistani population.
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