Origins and divergence of the Roma (Gypsies)

The identification of a growing number of novel Mendelian disorders and pri vate mutations in the Roma (Gypsies) points to their unique genetic heritag e. Linguistic evidence suggests that they are of diverse Indian origins. Th eir social structure within Europe resembles that of the jatis of India, wh ere the endogamous group, often defined by profession, is the primary unit. Genetic studies have reported dramatic differences in the frequencies of m utations and neutral polymorphisms in different Romani populations. However , these studies have not resolved ambiguities regarding the origins and rel atedness of Romani populations. In this study, we examine the genetic struc ture of 14 well-defined Romani populations. Y-chromosome and mtDNA markers of different mutability were analyzed in a total of 275 individuals. Asian Y-chromosome haplogroup VI-68, defined by a mutation at the M82 locus, was present in all 14 populations and accounted for 44.8% of Romani Y chromosom es. Asian mtDNA-haplogroup M was also identified in all Romani populations and accounted for 26.5% of female lineages in the sample. Limited diversity within these two haplogroups, measured by the variation at eight short-tan dem- repeat loci for the Y chromosome, and sequencing of the HVS1 for the m tDNA are consistent with a small group of founders splitting from a single ethnic population in the Indian subcontinent. Principal-components analysis and analysis of molecular variance indicate that genetic structure in exta nt endogamous Romani populations has been shaped by genetic drift and diffe rential admixture and correlates with the migrational history of the Roma i n Europe. By contrast, social organization and professional group divisions appear to be the product of a more recent restitution of the caste system of India.