The varied arrangement of the alpha globin genes in alpha thalassemia and Hb H disease in American blacks.

Both Eco RI and Eco RI x Bam HI restriction endonuclease digests of DNA from black Americans with alpha thalassemia yielded an alpha-specific fragment 4 kb shorter than in normals. In Hb H disease, only the shorter fragment was noted, while in "silent carriers" (alpha-thal 2 trait), both the normal and shorter fragments were detected. One subject with single gene deletions on both homologous chromosomes (alpha-thal 1 phe. A non-deletional form of alpha thalassemia also was discovered.