Physical mapping of the globin gene deletion in (delta beta (0)) -thalassaemia.

We have constructed a physical map of restriction endonuclease cleavage sites in the (delta (+) beta)-globin gene region in the DNA of patients with (delta beta(0))-thalassaemia. This map shows that a 10 kb deletion has occured in (delta beta (0))-thalassaemia to remove the entire beta-globin gene and the 3' portion of the delta-globin gene. The 5' terminus of the deletion is in the large intron of the delta-globin gene and the 3' terminus 1.8 kb to the 3'-side of the beta-globin gene. A similar deletion of about 7 kb has been described previously in the DNA of patients with Hb Lepore; the 5' terminus of the deletion is also in the delta-globin gene but the 3' terminus is in the beta-globin gene. Comparison of the foetal (gamma) globin gene expression in adults with (delta beta(0))-thalassaemia and Hba Lepore suggests that the 3' extragenic regions of the beta-globin gene contain DNA sequences involved in the regulation of gamma-globulin gene expression.