A new polymorphism in the β-globin gene is described, using the restriction enzyme Asu I. A radioactive probe specifically representing the large intervening sequence (IVS 2) of the β-globin gene has been used to detect this polymorphism. Normally, a 0.8-kilobase fragment containing β-IVS 2 is generated by Asu I; however, a 1.0-kilobase fragment is seen in association with 18% of β(A)-genes, and 38% of β-thalassemia genes in an Israeli population studied. By contrast, the Asu I polymorphism has rarely been seen in blacks examined to date. An additional Asu I change is seen a δ-IVS probe. The β-Asu I polymorphism is shown to be useful in the antenatal diagnosis of β-thalassemia.
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