Forensic parameters of the Powerplex® 21 system (Promega Corp.) in mestizo populations from the West of Mexico

Abstract

IntroductionMicrosatellites or short tandem repeats (STR) are the markers of choice in human identification. For this purpose, they must be analyzed in populations. This task has been scarcely performed for new generation human identification systems, which is critical in Mexican mestizo populations, because a significant genetic structure has been demonstrated due to admixture differences. ObjectiveTo validate the system in mestizo populations from the west region of Mexico. MethodsA total of 374 unrelated Mexican-mestizos from the west region were analyzed with the Powerplex® 21 system. Genetic data were analyzed using different softwares and including additional related populations for comparison purposes. Results and conclusionsWe estimated allele frequencies, and genotype distribution of all markers was in agreement with Hardy-Weinberg expectations; the linkage disequilibrium test discarded association between all pair of loci. The following forensic parameters were estimated: power of discrimination (PD), power of exclusion (PE), heterozygosity (Het), polymorphism information content (PIC), and typical paternity index (PI); its combined power of discrimination and exclusion was –100% and 99.999999473%, respectively. This constitutes an important increment with respect to typical 15 STR systems for the same population/region. This report validates the Powerplex® 21 system in western Mexican-mestizos for confident interpretation of DNA profiles in forensic cases and paternity testing. Sistema Powerplex® 21; México; Identificación humana; Poblaciones.