Beta-globin gene polymorphism in the Saudi Arab population.

DNA mapping with the restriction endonucleases, Hpa I and Mst II, has been used to investigate beta-globin gene polymorphism in the Saudi Arab population. Using Hpa I digestion, 13.0 kb and 7.6 kb fragments were found in association with the beta A and beta S genes. The frequency of the polymorphic forms in two regions investigated vary significantly. In Al-Hafouf and the surrounding villages, situated in the Eastern Province of Saudi Arabia, the frequencies of association of the beta A gene with the Hpa I 7.6 kb, 7.0 kb, and 13.0 kb fragments were 0.866, 0.043, and 0.071, respectively. The frequency of association of beta S with the 7.6 kb and 13.0 kb fragments resulting from the Hpa I digestion were 0.875 and 0.125. In Khaiber, Tehamat-Aseer, and surrounding villages, in the Western Province, the frequency of association of beta A with 7.6 kb, 7.0 kb, and 13.0 kb fragments were 0.836, 0.027, and 0.0136, respectively, while that of beta S was 0.250 and 0.750 with 7.0 kb and 13.0 kb Hpa I fragments, respectively. Using Mst II digestion, beta A was found to be linked to a 1.15 kb fragment, while beta S was linked to a 1.35 kb fragment. The normal (Hb AA), heterozygotes (Hb AS), and homozygotes (Hb SS) gave 1.15, 1.15/1.35, and 1.35 kb fragments, respectively. The results of this study show extensive polymorphism at the Hpa I restriction site of the beta A and beta S globin genes with the different polymorphic forms existing at a variable frequency in different regions of Saudi Arabia.