DNA-SEQUENCE VARIANTS IN THE G-GAMMA-GLOBIN, A-GAMMA-GLOBIN, DELTA-GLOBIN AND BETA-GLOBIN GENES OF MAN

DNA prepared from 60 unrelated individuals was cleaved with one of eight different restriction endonucleases and the resulting DNA fragments were separated by agarose gel electrophoresis. DNA fragments containing Gγ-, Aγ-, δ- or β-globin genes were detected by Southern blot hybridization, using as probe either a 32P-labeled cloned DNA copy of rabbit β-globin messenger RNA or labeled human β- and Gγ- globin cDNA plasmids. Three types of variant restriction enzyme patterns of globin DNA fragments were detected in otherwise normal individuals. One variant pattern, found in only one person, was caused by an additional restriction endonuclease Pst I cleavage site in the center of the δ-globin gene intervening sequence; the subject was heterozygous for the presence of this cleavage site and was shown to have inherited it from her mother. Another variant pattern resulted from the appearance of an endonuclease Hind III cleavage site in the intervening sequence of the Aγ-globin gene; this variant is polymorphic, with a gene frequency for the presence of the intragenic Hind III site of 0.23. This Hind III cleavage site polymorphism is also found in the Gγ-globin gene intervening sequence, and thus the polymorphism itself appears to be duplicated over the pair of γ-globin loci. These variants can be used to derive an approximate estimate of the total number of different DNA sequence variants in man. © 1979.