Genetic factors involved in human G gamma and A gamma globin gene expression

G gamma to A gamma globin ratios, haplotypes at the beta globin gene cluster and the C----T substitution at -158 5' to the G gamma globin gene were studied in three Algerian families that include SS or S-beta(0) thal patients. G gamma to A gamma ratios were found similar, within a family, in subjects displaying the same combination of chromosomes 11, the ratio observed for a given combination depending on the chromosome haplotypes. Our data can be explained by the existence of several alleles of a genetic factor closely linked to the beta globin gene cluster and involved in the determination of G gamma to A gamma globin ratio.