Sometimes, forensic scientists only have mtDNA to work with in their evidence samples, with examples being old bones and hair shafts. However, because this genetic information is passed down from a person’s mother, an individual will have the same mtDNA as his or her mother and siblings, making it hard to distinguish between members of the same family. As a result, it can be challenging in some cases to use mtDNA for identification in forensic investigations.
Penn State scientists will use the $430,000 NIJ grant to explore the rates of low-level mixtures of mtDNA found in most individuals, called heteroplasmic variants. These variants are areas of genetic information in mtDNA that can differ between a mother and child, or between siblings, making this type of DNA analysis much more informative for forensic identifications. In addition, the scientists at Penn State will evaluate how variants are passed between relatives, and between different tissue types in a person’s body. Their initial findings on this topic were published recently in the Proceedings of the National Academy of Sciences.
This research project showcases an interface between biology and forensic science research, said Mitchell Holland, associate professor of biochemistry and molecular biology, and the lead investigator on the grant. “It’s basic research that helps us understand the rates of these low-level mtDNA variants, and how they move between maternal relatives and different tissues in a person’s body. While these are basic questions of interest to biologists, they also have direct applications to forensic science,” he said.
The investigators will apply next-generation sequencing technologies to explore the mtDNA variants. Next-generation sequencing allows a scientist to obtain much more genetic information than traditional sequencing methods and is allowing forensic scientists to explore areas of mtDNA genetics that weren’t particularly feasible before, said Holland, and the technology is growing fast. “Sequencing technology is growing at a faster rate than computer technology, which is incredible.”
The aim of the research is to make mtDNA analysis a much more useful tool in forensic investigation by providing more information from an mtDNA testing result. The potential impacts of this research are broad and far reaching for the forensic community, and could increase the value of mtDNA evidence in forensic casework.