Genealogical Identification and Short Tandem Repeat-Based Verification of Suspected Consanguinity in Mongolian Families.

Purpose: The prevalence of consanguineous marriages remains high in several regions worldwide, particularly the Middle East and South Asia, with a reported rate of 58%. However, the prevalence and genetic characteristics of consanguineous marriages in Mongolia are not well studied. This study aimed to estimate the frequency of consanguineous marriages in selected Mongolian populations, using genealogical and short tandem repeat (STR) analyses. Patients and Methods: This cross-sectional study was conducted at the Institute of Biomedicine at the Mongolian National University of Medical Sciences. A total of 574 individuals from 185 families across 43 soums in three provinces (X1, X2, and X3) were included. Genealogical analysis was used to construct pedigree-based consanguinity profiles, and STR analysis was performed to validate biological relatedness in selected families. Results: Seventeen families were consanguineous, with a mean inbreeding coefficient of 0.089 ± 0.136, whereas 42 families were classified as suspected consanguinity. Among the confirmed cases, seven families with complete biological samples were further analyzed using STR markers, of which five showed molecular evidence of consanguinity (probabilities, 76.18-98.84%). The STR analysis of 29 families classified as suspected or non-consanguineous identified 13 families as non-consanguineous and 10 families showing possible or indeterminate relatedness. Notably, six families initially classified as suspected or non-consanguineous demonstrated molecular evidence of consanguinity (probabilities, 70.75-99.85%). Genetic diversity analysis revealed reduced heterozygosity in offspring from consanguineous families (expected heterozygosity [HE] = 0.7580, observed heterozygosity[HO] = 0.7045) compared with offspring from non-consanguineous families (HE = 0.7858, HO = 0.8110), with a significant reduction in HO ( Conclusion: This study demonstrates the value of integrating genealogical and STR-based molecular approaches for the assessment of consanguinity in Mongolia. Molecular analyses identified consanguineous relationships that were not evident from pedigree information alone and revealed reduced genetic diversity among offspring from consanguineous families. These findings provide important baseline data for understanding the genetic consequences of consanguinity in the Mongolian population and support the need for large scale epidemiological and genetic investigation.