Structural analysis of the alpha-globin gene cluster in two Chinese families with alpha-thalassemias.

: The inheritance of alpha-thalassemia is determined by restriction endonuclease mapping in the members of two Chinese families with history of Hb H disease. One family carries the South East Asia (SEA) deletion in alpha-thalassemia-1 determinant and the nondeletion mutation in alpha-thalassemia-2 determinant. The other family carries the SEA deletion in alpha-thalassemia-1 determinant and the leftward deletion in alpha-thalassemia-2 determinant. Direct analysis of the genetic defects by gene mapping technique is the most reliable method for detecting minor forms of alpha-thalassemia and provides valuable information for genetic conseling in affected families.