The interaction of alpha-thalassaemia and haemoglobin G Philadelphia.

An American Negro woman was found to have HbH disease in association with HbG Philadelphia (alpha68-asn leads to lys). Starch gel electrophoresis failed to reveal the presence of any HbA or HbA2 and studies of globin chain synthesis indicated absence of alphaA production. The alphaG/beta synthesis ratio was 0.63. The woman's son and her two half-sibs had alpha-thalassaemia trait with no HbH and alpha/beta synthesis ratios of 0.84, 0.84 and 0.76. The data indicate that there is no functioning alphaA gene linked to the alphaG gene. The absence of alphaA synthesis by the propositus also indicates that the alpha-thalssaemia gene trans to the alphaG gene completely suppresses alpha chain production, the first evidence for such a gene in Negroes.