Evaluation of genetic parameters affecting the reliability and effectiveness of kinship reconstruction in Forest and Tundra Nenets populations using X-STR markers

X-chromosomal STR markers (X-STR) are informative tools for kinship reconstruction, particularly in cases  where standard autosomal panels have limited discriminatory power: when reconstructing kinship between full sisters, paternal half-sisters, paternal grandmother and granddaughter, maternal aunt and niece. However, the use of X-STR markers in forensic genetics requires consideration of linkage disequilibrium structure and the use of haplotype frequencies in calculating the likelihood ratio (LR). In this work, the genetic structure of Forest and Tundra Nenets populations was assessed using 16 X-STR markers in order to obtain reference values. A sample of 504 Nenets males was analyzed, divided into subethnic groups (Forest and Tundra Nenets), phratries of Tundra Nenets (Haryuchi and Vanuito), as well as geographical local groups (individuals living in the Antipayutinskaya, Gydan and Nakhodka tundras). No statistically significant differences were found between the samples, and the pairwise Fst values (exact test) did not exceed 0.01. The Nenets population demonstrated an intermediate level of genetic diversity typical of Indigenous  Siberian populations. The loci DXS8377 (He = 0.910) and DXS10079 (He = 0.839) were found to be the most polymorphic in the Nenets population. Of the 16 markers, 13 were highly informative (PIC > 0.5). The combined power of exclusion (CPE) was 0.99996, which indicates that the panel is highly informative for reconstructing kinship relationships. Pairwise analysis of linkage disequilibrium (LD) revealed statistically significant deviations for 46 pairs of markers out of 120; however, the r² coefficient for all pairs of alleles did not exceed 0.09, which indicates a weak correlation between alleles. This study provides the reference data of allele and genotype frequencies recommended for use in assessing the likelihood ratio in the reconstruction of kinship relationships. The obtained reference data will contribute to improving the reliability and efficiency of forensic genetic analyses in the Russian Federation. 

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