Restriction endonuclease mapping of the human gamma globin gene loci

The restriction endonuclease sites in and around the human gamma globin gene loci have been mapped using the gel blotting technique of Southern, in both normal DNA and DNA from an individual with hereditary persistence of fetal hemoglobin (HPFH). In normal DNA, the gamma genes are linked to the delta (and beta) globin genes, and the orientation of these genes with respect to transcription is (5') G gamma leads to A gamma leads to delta leads to beta (3'). The distance between the G gamma and A gamma genes is 3.5 kb and that between the A gamma and delta genes is 16 kb. In both normal DNA and HPFH DNA, the gamma genes are interrupted by an intervening sequence, approximately 1 kb in length that is situated between codon positions 99 and 121 of the coding sequence. In different DNA samples, there is polymorphism for the presence or absence of a Hind III site in the intervening sequence of either gamma golbin gene. In HPFH DNA, a deletion of at least 16 kb of DNA has been detected. This deletion starts at a point approximately 12.5 kb from the 3'-end of A gamma gene and extends through the delta and beta globin genes to a point at least 3 kb beyond the 3'-end of beta globin gene.