Genetic markers in Welsh gypsies.

Data are presented on polymorphic genetic markers of 84 Welsh gypsies, members of an inbred population characterised by a high incidence of phenylketonuria and other recessively inherited diseases. Sixteen polymorphic loci were studied: the ABO blood group distribution was comparable to that of the surrounding population, the B gene frequency being 7-5%, a lower frequency than most earlier studies in gypsies. The haptoglobin 1 gene frequency (23-7%) was very different from that of the British population, resembling the frequency found in India and some previously reported gypsy groups. The data on Welsh gypsies for the various loci are discussed in relation to the known evidence for a number of European gypsy populations, and in relation to the genetic structure of these populations. It is concluded that genetic divergence has occurred in the European gypsies, and that this may have been accentuated by the dispersal, isolation, and inbreeding which have occurred during the present century.