Fetal haemoglobin consists of α- and γ-chains. There are two types of human γ-chains:one, (Gγ) in which residue 136 is one of glycine, and another (Aγ), in which that position is occupied by a residue of alanine. Some time ago a homozygote for the high persistent fetal haemoglobin gene was found in Ghana whose sole red cell pigment was fetal haemoglobin. The nature of the fetal haemoglobin in this individual has now been determined. It is entirely of the Gγ-type.
The clinical and haematological data of nine patients with haemoglobin H disease, as well as of 16 members of their families, are reported. Pedigree study and haematological data permit the assumption that in an individual four genes could be responsible for α-chain synthesis. Based on this hypothesis, four variants of α-thalassaemia are expected to exist. The first, in which only one gene is affected has no, or only minor, red cell changes and an increase in Hb Bart’s at birth, the second with two genes affected has in addition Hb H inclusion bodies in a few red cells, the third, with three genes affected represents haemoglobin H disease, and the fourth, with all four genes affected, represents homozygous α-thalassaemia, which is incompatible with life and results in a stillborn child with hydrops foetalis.
The γ chain in a Ghanaian homozygous for hereditary persistence of fetal haemoglobin was considered to be of the Gγtype on the basis of the amino acid analysis of γTp XIV (γ133–144) of the Hb F of this subject [1]. Recently, the sequence of residues γ134–137 of the γ-chain of this subject was determined and found to contain some alanine at position γ136. It is therefore of the Gγ + Aγtype. A rapid technique for the isolation of γCB-3 (γl34–146) peptides in human fetal haemoglobin for Gγ;Aγratio determination is described.
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