Expanding beyond the current core STR loci: An exploration of 73 STR markers with increased diversity for enhanced DNA mixture deconvolution. (January 2019)

• Record Type: Journal Article
• Authors: Novroski, Nicole M.M.; Wendt, Frank R.; Woerner, August E.; Bus, Magdalena M.; Coble, Michael; Budowle, Bruce
• Is Part Of: Forensic science international. Volume 38(2019)
• Page Start: 121
• Page End: 129
• Publication Date: 2019-01
• Subjects: Short tandem repeats -- Sequence variation -- DNA mixtures -- Mixture deconvolution; Forensic genetics -- Periodicals; Génétique légale -- Périodiques; Forensic genetics; Electronic journals; Periodicals; 614.1
• DOI: 10.1016/j.fsigen.2018.10.013
• Languages: English
• ISSNs: 1872-4973

Abstract

Highlights: Study describes population data on 73 highly informative STRs. Study compares selected top 20 performers of these novel STRs with the CODIS core loci for qualitative mixture resolution. In silico allele counting of pairwise mixtures performed for 443 samples from three major populations for each locus and for all DNA profiles. In silico comparison of core CODIS markers ( n = 20) to a subset of 73Plex markers ( n = 20; 20Plex) as well as a combination of the top loci ( n = 20) from both panels. Utilizing a combination of STR 20Plex markers ( n = 17) in conjunction with top performers of the CODIS core markers ( n = 3), a 32-point % increase in full resolution of component contributors was observed. Abstract: Current approaches to mixture deconvolution of complex biological samples at times do not have the capability to resolve component contributors in DNA evidence. Additional short tandem repeat (STR) loci were sought that may improve the forensic genetic analysis of mixtures. This study presents exploratory data of a multiplex comprised of 73 highly polymorphic STRs (referred herein as the 73Plex) that were selected because of their high diversity due to sequence variation. These STRs (or a subset of them) may be considered as candidates that may augment current core markers capabilities for DNA mixture deconvolution. Population genetics analyses were performed for each locus using DNA samples from 451 individuals comprising three U.S. populations. Sequence-based heterozygosities ranged from 72% to 98%, where only two loci (D10A97 and D6A7) fell below 80%. Mixture deconvolution capabilities for two-person mixtures were assessed based on complete allele resolution per locus (i.e., four alleles observed) of pairwise mixtures using in silico methods. A subset of 20 highly informative loci (referred herein as the 20Plex) from the 73Plex was compared to the 20 CODIS core loci on all population samples with full DNA profiles for both panels (i.e., no locus dropout; n = 443). Based on proportion of loci displaying four alleles, the 20Plex outperformed the CODIS core loci with increases of 82.6% and 89.3% using length-based and sequence-based alleles, respectively. A combination of 17 STR from the 20Plex and 3 CODIS loci gave the highest capacity for resolving allelic components per locus. These data illustrate the increased value of utilizing sequenced-based alleles of additional STR loci. Furthermore, there are a number of candidate STR loci that could notably augment the current core STR loci and enhance mixture interpretation capabilities.