Swedish population data for 37 autosomal, 12 X-chromosomal and 23 Y-chromosomal STR loci.

Population genetic analysis is a fundamental component in forensic genetics for ensuring the reliability and validity of DNA evidence interpretation. Here, we present a comprehensive forensic genetic analysis of a contemporary Swedish population, based on 37 autosomal, 12 X-chromosomal and 23 Y-chromosomal short tandem repeat (STR) loci. Blood samples were systematically collected from individuals across all 21 counties of Sweden. Five commercial forensic STR kits (PowerPlex Fusion 6C System, PowerPlex Y23 System, Investigator HDplex kit, Investigator X12QS kit and Mainstay SE) were analysed. In total, autosomal STR allele frequencies were generated from 538 individuals, and X- and Y-chromosomal haplotypes were established from 513 males. High genotype concordance (> 99.95%) was observed across overlapping loci between kits, confirming the robustness and reliability of the investigated systems. A few discrepancies were identified, primarily due to STR nomenclature differences between capillary electrophoresis and sequencing generated alleles. Both fragment length-based and sequence-based allele frequencies were obtained. Statistical analysis revealed high discriminatory power, no signs of deviations from Hardy-Weinberg equilibrium, and no evidence of linkage disequilibrium between any pair of loci. Minimal genetic differentiation was observed within Sweden and between Sweden and geographically close populations, whereas significant genetic differences were found when comparing with more distant populations. These findings confirm that the analysed STR loci are well suited for forensic applications in the Swedish population. The resulting allele and haplotype frequency data establish an updated and expanded population-specific reference database, which is expected to serve as a valuable resource for forensic casework in Sweden.