Mitochondrial DNA Analysis in Human Identification

Imagine that you have a small, aged bone fragment or charred remains after a fire, a tooth that has been buried and exposed to the environment for years to decades, or possibly a single hair shaft. How would you even begin to make an identification to reconnect these remains with family members? In these small and compromised samples, often nuclear DNA is insufficient to generate useful results with current STR typing methods. Since the early 1990’s, mitochondrial DNA (mtDNA) analysis has been used in these most challenging of cases. Human cells contain only two copies of nuclear DNA, but can contain roughly 500-1000 copies of the small mtDNA genome (16.5 kb). To date, most mtDNA analyses have focused on the Control Region (CR), a highly polymorphic 1.2 kb stretch that consists of hypervariable regions I, II and III (HV-I, HV-II and HV-III), using Sanger sequencing to assist with human identifications. Control region analysis, however, may result in inconclusive identifications due to the maternal inheritance of the mtDNA genome and lack of genetic recombination. With the introduction of the Applied Biosystems™ Precision ID NGS System and the Precision ID mtDNA Whole Genome Panel, which uses a unique tiling approach to cover the entire genome, mtDNA genome analysis offers increased discriminatory power, resulting in more unique haplotypes to aid in better identifications. Bodner, et al demonstrate the utility of mtDNA whole genome sequencing for forensic applications and here Walther Parson from the Institute of Legal Medicine, Innsbruck Medical University discusses a number of cases his lab has worked on, using mtDNA analysis to make critical identifications.