Characterization of forensic DIP-STR markers in the admixed population of Córdoba, Argentina

Abstract

To genotype the minor component in two-person DNA mixtures with ratios greater than 15:1, researchers have described the use of autosomal markers known as DIP-STRs. These markers combine a biallelic deletion (S-DIP) or insertion (L-DIP) polymorphism physically linked to a nearby STR. This methodology enables the detection of minor DNA components present at up to 1,000-fold lower quantities than the major contributor. DIP-STR markers have been thoroughly characterized in the Swiss population, to a lesser extent in the Han Chinese and Polish populations, but no studies have been conducted in Latin American populations. Here, we investigated DIP-STR markers in the population of Córdoba, Argentina, by determining the allele frequencies of DIP-STR haplotypes in 100 individuals from different regions of the province. Among the 23 markers analyzed, 21 exhibited a high probability of being informative in this population, comparable to that observed in European populations, thus supporting the applicability of this strategy for resolving highly unbalanced DNA mixtures. Additionally, DIP-STR haplotypes were analyzed to infer biogeographic origin, using the Bayesian clustering algorithm Structure, with the HGDP-CEPH panel as reference population. The results revealed a clear distinction among major continental regions, with significant ancestral contributions of European, followed by Native American, and African origin. These findings are consistent with the regional demographic history and underscore the effectiveness of the haplotype approach for ancestry-informative markers in the Argentine population. In conclusion, DIP-STRs represent a valuable forensic tool, combining mixture deconvolution with biogeographic ancestry inference.