Application of DNA polymorphisms for prenatal diagnosis of β thalassemia in chinese

Forty‐seven Chinese suffering from β thalassemia major and their parents were studied to establish linkage of the β thal and β A genes with 11 restriction site polymorphisms. There is marked linkage disequilibrium at the BamH I site 3′ to the β globin gene, such that, in 31% of pregnancies, absence of the site in the fetus can exclude β thalassemia major. Using four restriction sites (Hinc II β, Ava II β, Hind III β, and BamH I β), prenatal diagnosis is feasible in all families. In 46% of all cases, a definitive diagnosis can be made, and in the remaining cases, a 50% chance of exclusion is possible. Fetal blood globin chain analysis would be required for the failures. Our experience in nine successive β thalassemia prenatal diagnosis is also reported.