Allele frequency distribution and forensic efficiency parameters of 24 autosomal STR markers in the santhal tribal community of Bihar, India

Abstract

This article reports the allele frequency distribution and statistically calculated the forensic efficiency parameters of 210 unrelated volunteers that belong to a specific tribal group named Santhal living in Bihar, India. 24 specific short tandem repeat (STR) markers are included in this study by using the Ingenomics™ AutoProfiler STR Kit. The Power of discrimination (PD), power of exclusion (PE), observed heterozygosity (Ho), expected heterozygosity (He) polymorphism information content (PIC), probability of match (PM), typical paternity index (TPI) and Hardy–Weinberg equilibrium (HWE) p-value were calculated. The result shows that the probability of match (PM) values across the loci ranged from 0.012 to 0.186, while the power of discrimination (PD) varied from 0.814 to 0.988. The highest PD values were observed at SE33 (0.988), Penta E (0.983), and FGA (0.962), indicating their strong ability to differentiate individuals within the population. Conversely, loci such as CSF1PO (0.814) and D2S441 (0.844) showed comparatively lower discrimination power. The polymorphism information content (PIC) values ranged from 0.601 to 0.933, with most loci showing PIC values greater than 0.7, reflecting a high degree of polymorphism. Gene diversity values were also high across the studied loci, ranging from 0.666 to 0.939, further confirming the substantial genetic variability present in the population. The power of exclusion (PE), which is an important parameter for paternity testing, ranged from 0.428 to 0.913, with SE33 and Penta E showing the highest exclusion capacities. The typical paternity index (TPI) values varied from 1.667 to 11.667, again highlighting the strong contribution of highly polymorphic loci such as SE33, Penta E, and D12S391. The combined probability of match (CPM) was 2.41 × 10⁻²⁸, combined power of exclusion (CPE) was 0.999999999991, combined paternity index (CPI) was 3.51 × 10¹⁰ and combined power of discrimination was 1 providing very strong statistical support for the application of these markers in paternity testing. These results demonstrate that the 24 autosomal STR loci possess high forensic efficiency and are highly informative for forensic identification and kinship analysis in the santhal population.