Linkage between fetal A gamma globin chain polymorphism and DNA polymorphism of the human beta gene cluster in beta thalassaemia.

The association between the polymorphism of the A gamma chain of human fetal haemoglobin and the DNA polymorphism at the beta gene cluster has been investigated. The A gamma 75 threonine mutation was found in association with haplotypes II and VI described by Orkin et al. (1982), which share the HindIII cleavage site in the A gamma IVS 2 sequence. The distance between the two polymorphic sites is 868 base-pairs. In contrast, haplotypes I, III, V and IX which do not possess this HindIII cleavage site were associated with the normal A gamma 75 isoleucine allele. The simple detection of the gamma gene polymorphism at the protein level can be useful for identifying DNA haplotypes, and therefore beta thalassaemic mutations.