Forensic scientists need to differentiate genetic profiles from complex forensic DNA mixtures, such as those commonly associated with crime scenes. But complicating factors, such as DNA degradation, mixtures and/or insufficient starting material, may prevent an estimated 30-40 percent of samples from generating conclusive results when using traditional capillary electrophoresis-based approaches. Now, by using the Applied Biosystems Precision ID GlobalFiler NGS STR Panel v2 and Converge Software 2.0, labs can effectively retrieve more information from these mixed, degraded or limited DNA samples. The increased HID STR genotyping functionality provides information on length-based STR allele call, sequence-based repeat motif, known SNPs in flanking regions, and isometric heterozygote (alleles of the same fragment length, but containing different repeat sequence) information. These additional sequence-based characteristics can deliver a wider allele range with an increased power of discrimination for individual identification.
Dr. Pedro Barrio, a DNA expert with the National Institute of Toxicology and Forensic Sciences in Madrid, Spain, participated in the early access program for this new STR sequencing technology. Dr. Barrio is also involved with the DNASEQEX project, and serves as a coordinator of the Mixture Commission of GHEP-ISFG (Spanish and Portuguese Speaking Group of the International Society on Forensic Genetic). This experience in working with mixtures allowed Dr. Barrio to test the limits to get more information from his samples. Watch Dr. Barrio’s interview from Thermo Fisher Scientific’s HIDS 2017 event.