A heterozygote for Hb S beta, Hb C beta and Hb G Philadelphia beta in a family presenting evidence for heterogeneity of hemoglobin alpha chain loci.

A child heterozygous for the genes for hemoglobins S, C and G alpha Philadelphia presented with a clinical picture similar to sickle cell anemia. Her hemoglobin electrophoretic pattern contained three components with the mobilities of hemoglobins S (35 per cent), C (47 per cent) and a more slowly migrating hybrid G/C molecule (15 per cent). Seven relatives were heterozygous for Hb G beta and Hb S beta and five were heterozygous only for Hb G alpha. Among the latter, three had approximately 30 per cent and two had 40 per cent of Hb G. These proportions are consistent with the hypothesis that the American Negro genome contains two types of chromosomes bearing structural loci for alpha chains, some possessing one Hb alpha locus, others having two loci. Hb G alpha-Philadelphia presumably arose as a mutation on a chromosome with a single locus. Those heterozygotes having 30 per cent and 40 per cent Hb G presumably have two loci and only one locus, respectively, on the homologous chromosome.