The Genetic Structure of the Romanian Male Population Revealed by 27 Y-Chromosome STR Loci

Y-chromosomal Short Tandem Repeats (Y-STRs) provide insight into forensic evidence interpretation and male population history. Romania's position at the crossroads of Europe and Western Asia makes it a key reference population for both domains, yet existing Romanian Y-STR databases are limited in geographic coverage and marker number. We genotyped 928 unrelated Romanian males across all 41 counties and Bucharest at 27 Y-STR loci using the Investigator Argus Y-28 Kit, and modeled haplotype frequencies using the Discrete Laplace (DL) distribution (disclapmix v1.7.5, 17-locus panel; disclapmix2 v0.6.1, 27-locus panel). Discrete Laplace modeling revealed 12 and 14 optimal mixture components for the 17- and 27-locus models, respectively, with median match probabilities of 1 in 1.25 × 10⁷ and 1 in 5.8 × 10¹², reflecting nearly six order-of-magnitude gain in evidential weight. Haplogroup analysis identified 16 Y-lineages; R1a, I2a, E1b1b, J2a, and R1b collectively represent ~80% of the population, and reflect Romania's layered Steppe, Balkan, and Near Eastern ancestry, with subtle regional gradients between Moldavia, Transylvania, and Muntenia. This dataset provides validated forensic reference data and new insights into the patrilineal genetic structure of the Romanian population.