The interaction of alpha thalassaemia with heterozygous beta thalassaemia.

The alpha globin genotypes of 55 beta thalassaemia heterozygotes have been determined by restriction endonuclease analysis to identify those with interacting alpha thalassaemia genes. A comparison of the haematological and haemoglobin synthesis findings of individuals with normal alpha genotypes (alpha alpha/alpha alpha) with those with one (-alpha/alpha alpha) or two (-alpha/-alpha) alpha genes deleted shows that the latter two groups have more balanced globin chain synthesis ratios, higher haemoglobin levels, and larger, better haemoglobinized red cells. This suggests that the degree of globin chain imbalance is a significant factor in determining the red cell characteristics in heterozygous beta thalassaemia.

Genetic and molecular diversity in nondeletion Hb H disease.

Restriction endonuclease mapping of nondeletion alpha-thalassemia determinants from a variety of racial groups showed no detectable abnormalities within a 40-kilobase region of the zeta-alpha globin gene cluster. By using a zeta-specific probe, we defined three different types of interactions that give rise to Hb H disease, each involving a nondeletion alpha-thalassemia haplotype. mRNA analysis showed further diversity within these groups, indicating that there are at least three nondeletion determinations.