An alternate workflow for preparing Precision ID Ancestry and Identity Panel libraries for Illumina sequencing

Single nucleotide polymorphisms (SNPs) are well-established for forensic applications. Although they are not compatible with existing criminal databases, they offer some advantages over short tandem repeat (STR) markers including smaller amplicons, no stutter artifacts, and biogeographic ancestry and phenotype predictions. The Precision ID NGS System, a commercial workflow by Thermo Fisher Scientific, offers a streamlined solution for genotyping forensically relevant SNPs using next-generation sequencing. The Precision ID Ancestry and Identity Panels combined target 289 SNPs, and their sensitivity, reproducibility, and accuracy have been evaluated by the forensic community. The aim of this study was to develop an alternative workflow to genotype these SNP panels using Illumina chemistry. Commercial genomic DNAs (gDNAs) (n, 3) were amplified using three uracil-tolerant polymerase master mixes. Resulting amplicons were prepared into libraries using the KAPA Hyper Prep Kit (KAPA Biosystems) and sequenced via Illumina's MiniSeq. Reads were analyzed using a published analysis pipeline to compile final genotypes with read depth information. Phusion U Multiplex PCR Master Mix (Thermo Fisher Scientific) statistically outperformed the other master mixes tested (P <0.0001), with respect to the number of SNPs genotyped. To ensure a workflow using Phusion U would be compatible across diverse samples, we optimized PCR cycle number using the same commercial gDNAs (n, 3), reference buccal swabs (n, 3), and environmental (household dust) samples (n, 6). Using the developed workflow, 93.9% of all SNPs were successfully genotyped across sample types. Implementation of the developed workflow should be straightforward for forensic laboratories and suitable for processing reference and casework samples.

Automated summary

Single nucleotide polymorphisms (SNPs) have value in forensic applications, offering advantages over short tandem repeat (STR) markers. Through the use of different polymerase master mixes, an effective workflow was developed to successfully genotype 93.9% of SNPs.