Molecular Identification of the some mtDNA SNPs in sample of Saudi population for forensic application

Mitochondrial DNA (mtDNA) is widely used for many years in forensic applications especially when nuclear DNA (ncDNA) is non-detectable. Recently, SNPs were proven to be reliable markers in distinguishing among closely related sequences. In the present study, SNPs were searched in the hypervariable regions I and II (HVI & HVII) of the human mitochondrial D-loop sequences of 100 and 400 maternally unrelated Saudi individuals within and among populations (four Saudi cities: Dhahran, Jeddah, Khamis mushait and Riyadh), respectively. The analysis resulted in the occurrence of 182 polymorphic sites derived from the 400 individuals differing in age, sex and race. Among 3107 nucleotide substitutions, transition showed higher rate in HVI region (47.80%) than transversion, while lower rate in HVII region (46.96%). Sensitivity testing of this type of markers indicated the random match probability (RMP) of as low as 0.75% with 269 haplotypes of which 211 were unique reflecting the high degree of diversity. For forensic applications, the mtDNA analysis was applied on 5 criminal cases - that were failed with STR analysis - using two experimental designs. The mtDNA analysis in both experiments I & II achieved 20% and 100% successful rate, respectively, compared to STR analysis that succeeded only in experiment I by 25% of the cases. The current study is the first of its kind in Saudi Arabia that applied the mtDNA analysis on real criminal cases in cooperation with the Directorate of Criminal Evidence in Jeddah/ Ministry of Interior, revealing the feasibility of using SNPs of the mitochondrial hypervariable regions as polymorphic resistance identifiers in forensic challenging samples of which many STR marker have failed to be employed.