P-Thalassaemia in a acid+valinePz) Coexisting with Caucasian Family

SUMMARY. Haemoglobin Inkster, a new a-chain variant, was discovered in a family which also had the gene for p-thalassaemia. The amino acid abnormality was in aTp-9 which contains 29 amino-acid residues. Structural studies were facilitated by cleavage of the abnormal a-chains with cyanogen bromide followed by tryptic digestion. The substitution was shown to be valine for aspartic acid at position 85 in the a-chain. Affected individuals had no haenlatological abnormalities. Individuals with both b-thalassaemia and Hb Inkster had slightly lower percentages of Hb Inkster than those found in persons heterozygous for the Hb Inkster gene alone. ‘Interaction ’ between thalassaemia and variant haemoglobin genes involving differ-ent haemoglobin loci has been reported in another family with f3-thalassaemia and an a-chain haeinoglobin mutant, as well as in the converse situation of coexisting a-thalassemia and a p-chain haemoglobin mutant. This decrease in the mutant haemoglobin percentage differs from the more common ‘interaction ’ of thalassaemia and mutant haemoglobin genes involving the same haemoglobin locus, in which the mutant haemoglobin percentage is increased. The mechanism for the ‘interaction