Ancestry informativeness of autosomal STRs using Massively Parallel Sequencing

The ability to estimate the geographic ancestry of a donor from a forensic sample can be of vital importance for so called “no-suspect, no-hit” cases. It is a tool that can provide information to law enforcement and enable prioritisation of specific lines of enquiry. Traditionally, this has relied on the use of specific ancestry informative single nucleotide polymorphisms (SNPs), run as an additional test to short tandem repeat markers (STRs). STRs have largely been discounted for geographic ancestry determination due to their high mutation rate, which in turn makes them well suited for individual identification. Being able to obtain a DNA profile that can simultaneously be used for geographical ancestry estimation and searching against offender databases would be a huge benefit to the field of forensic identification in terms of time, cost and sample availability.

The transition in forensics from capillary electrophoresis to massively parallel sequencing presents an opportunity to review the choice of genetic markers used for identification and assess the ways in which we utilise them. In relation to STR analysis, the move to assign alleles using sequence rather than length-based methodologies has highlighted the extent to which previous allelic variation was masked. In this work, 1000 samples from five global population groups were genotyped using the MiSeq FGx™ Forensic Genomics System. This presentation addresses the discovery and characterisation of novel sequence variants, and the opportunity to utilize this diversity in unique ways. In particular, the presence of population-specific sequence variation raises the prospect of using STR profiles for population identification, both on their own and in combination with ancestry-informative SNPs.