The restriction endonuclease sites in and around the human γ 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 γ genes are linked to the δ (and β) globin genes, and the orientation of these genes with respect to transcription is (5′) Gγ→Aγ→γ→β (3′). The distance between the Gγ and Aγ genes is 3.5 kb and that between the Aγ and δ genes is 16 kb. In both normal DNA and HPFH DNA, the γ 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 γ globin 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 Agamma; gene and extends through the δ and β globin genes to a point at least 3 kb beyond the 3′-end of β globin gene.
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