Forensic Genetics and the Differentiation of Monozygotic Twins by Mitochondrial DNA Analysis

Forensic genetics uses STR markers as the gold standard for human identification. However, this technique does not allow the differentiation of monozygotic twins, since they originate from the fertilization of a single egg and a single sperm. Studies aiming to solve this problem have been developed and the complete sequencing of mitochondrial DNA has shown to be relevant. The present study aimed to verify the possibility of differentiating monozygotic twins through the analysis of the d-loop region of mitochondrial DNA, using the Sanger sequencing technique in blood and oral mucosa samples. Twelve pairs of volunteer monozygotic twins were selected, zygosity was confirmed by analyzing the genetic profile generated using STR markers. Regarding analyses of the d-loop region of mitochondrial DNA, a single pair of twins (gm46) showed a point heteroplasmy at position 16,290 (HV1). However, this finding was not able to differentiate between individuals of the same pair, since both showed the heteroplasmy in both biological samples (blood and oral mucosa). No other genetic variation was detected in the pairs of twins analyzed that could differentiate them. We suggest analyzing the mitochondrial DNA molecule as a whole in an attempt to identify a greater amount of potential variation by applying the Massive Parallel Sequencing technique.