Preliminary population genetic analysis of 12 X-STR loci in a sample from Türkiye: allele frequencies, haplotype diversity, and linkage disequilibrium.

Background/aim: X-chromosomal short tandem repeats (X-STRs) are informative genetic markers in kinship testing and specific forensic contexts, particularly when standard autosomal approaches are less informative. This study aimed to provide preliminary allele frequency, haplotype diversity, and linkage disequilibrium (LD) data for 12 X-STR loci in a sample from Türkiye. Materials and methods: A total of 136 unrelated individuals from Türkiye were genotyped for 12 X-STR loci. Inferential analyses of X-linked loci require diploid genotypes; therefore, allele frequencies, Hardy-Weinberg equilibrium (HWE), LD, and regional comparisons were based primarily on female samples (n = 115), whereas male haplotypes (n = 21) were summarized descriptively only. Female regional subgroup sizes were uneven (southeast Anatolia, n = 39; Marmara, n = 22; Central Anatolia, n = 14; Mediterranean, n = 13; Black Sea, n = 10; Aegean, n = 9; eastern Anatolia, n = 8). Forensic parameters, HWE exact tests, and pooled and region-stratified LD analyses were calculated using Bonferroni-adjusted thresholds; findings were interpreted cautiously given the modest overall sample size and subgroup imbalance. Results: All loci were polymorphic, and locus-level forensic efficiency measures were generally high, with DXS10135 showing the highest informativeness in this dataset. In the female sample, five loci deviated from HWE after Bonferroni correction. In pooled LD analysis, only two of 66 locus pairs remained significant after correction (DXS10146-DXS10134 and DXS8378-DXS10103), whereas no region-specific LD signal remained significant after multiple-testing adjustment. Male haplotype diversity estimates were high across linkage groups, but these estimates were based on a small male subset and should be considered exploratory. Conclusion: This study provides a preliminary X-STR dataset for a sample from Türkiye and suggests that the analyzed panel is informative at the locus level. However, the modest sample size, very limited male subset, uneven regional distribution, and genotype-handling assumptions restrict population-level inference and generalizability. The data may be useful as an initial local reference resource, but broader and more balanced sampling is required before making strong conclusions about national allele distributions, regional structure, or routine forensic implementation.