Selection of an Ancestry-Informative Marker (AIM) Panel of INDELs

Purpose (a): In forensics, there are two main concerns with the marker systems currently used for human identification. First, the identification of the source of a biological sample found at a crime scene requires a comparison to a known reference sample. When no suspect is available for comparison, these genetic markers cannot provide any additional phenotypic information. In such cases, Ancestry-Informative Markers (AIMs) can be used as an investigative lead to law enforcement. A second issue commonly encountered is caused by sample degradation. When DNA is exposed to the elements, it can degrade to fragments of less than 200 base pairs (bps). The genetic markers currently used in forensic settings are called Short Tandem Repeats (STRs). The commercially available STR amplification kits generally yield amplified products that are 200-600 bps in length. Marker systems that yield short fragments. Methods (b): INDELs, insertions and deletions in the genetic sequence as compared to a consensus reference sequence, are a bi-allelic marker system that can be easily multiplexed and analyzed using the instrumentation currently available in forensic laboratories. In this project, publically available genome data was used to select a panel of INDELs that can distinguish between three major global population groups; Caucasian, African, and East Asian. The markers were selected based on specific criteria; length of INDEL, allele frequency divergence, population substructure, and genetic location. Results (c): "All INDELs were tested for departure from Hardy-Weinberg Equilibrium (HWE) and evidence of linkage disequilibrium (LD). Principal Component Analysis (PCA) of the markers indicate the AIMs ability to completely separate the three population groups. Additionally, analysis in STRUCTURE v2.3.4 gives statistical support for the presence of three separate population clusters. Conclusions (d): A robust panel of AIMs was chosen to distinguish between three major global population groups. By multiplexing these markers into a single reaction, the panel will provide a quick, reliable method for determining the ancestry origin of an unknown sample, which may provide significant benefits to forensic investigations.