Absence of Haemoglobin A in an Individual Simultaneously Heterozygous in the Genes for Hereditary Persistence of Foetal Haemoglobin and β‐Thalassemia°

Summary. Haemoglobins F and A2 are the only haemoglobins present in an American Negro adult who is simultaneously heterozygous in the genes for hereditary persistence of foetal haemoglobin (HPFH) and β‐thalassaemia°. About 15% of the haemoglobin F in descendants who are heterozygous only for HPFH is of the Gγ‐chain type. About 73% of the haemoglobin F in the HPFH‐β‐thalassaemia° heterozygote is of the Gγ‐chain type, and the fraction attributable to control cis to the β‐thalassaemia° gene in this individual is calculated to be entirely of the Gγ‐chain type. Thus synthesis of Aγ‐chain as well as of β chain is absent under control cis to this β‐thalassaemia° gene.