Genetic architecture of the Sindhi Indian population: a 19X-STR forensic analysis

Abstract

The X chromosome accounts for approximately 5% of the human genome and serves as a valuable marker in forensic and population genetics due to its uneven and asymmetrical pattern of inheritance. This unique trait enables significant applications, including kinship testing, half-sister paternity deficiency assessments, and analyzing relationships across generations. Notably, the unequal transmission of the X chromosome where females have two X chromosomes compared to males—contributes to sex-based disparities. The use of X-STRs offers additional evidence in cases where personal identification poses challenges in forensic investigations. In both population studies and forensic analyses, X-STRs are typically examined using commercially available kits, such as the Microreader 19X STR. The present study focuses on the Sindhi population, an ethnic group in India with ancestral roots in Pakistan. We analyzed 19 X-STR loci in the Sindhi Indian population, examining allele frequencies from 206 DNA samples derived from 144 unrelated males and 62 females. Among the 19 X-STR loci analyzed, DXS10135 showed the highest polymorphism with 19 observed alleles, while DXS7133 was the least polymorphic, with only 6 alleles. The Fst distance matrix analysis, which encompassed 26 global populations, revealed that the Sindhi Indian population shares the closest genetic affinity with Pathan, Baluchi, and other Pakistani groups, demonstrating an average genetic distance of approximately 0.006. These findings underscore the genetic proximity of the Sindhi population to Indo-European-speaking groups in the region. Notably, this study presents the first comprehensive X-STR reference dataset for the Sindhi population in India, providing novel data for forensic applications and enhancing the understanding of regional population structure and differentiation in South Asia. © The Author(s) 2025.