Mapping the alpha-globin genes in Hb J Mexico carriers.

The organization of the alpha-globin genes was studied by restriction endonuclease mapping, in subjects carrying the alpha variant Hb J Mexico. A subject homozygous for Hb J synthesized both Hb J (about 55%) and Hb A and had two alpha loci per chromosome. His restriction site map was found to be identical to that obtained with a normal DNA, except for a mutant Bgl II site which was observed on the Hb J chromosome proximal to the 5' alpha-locus. We have also mapped the DNA of a compound heterozygote for Hb J and alpha-thalassemia, who synthesizes 38% Hb J and we have found a single alpha gene corresponding to a - alpha 3.7 haplotype on one chromosome and two alpha genes, respectively alpha J and alpha A, on the other.