Negro alpha-thalassaemia is caused by deletion of a single alpha-globin gene.
Studies in two Jamaican Negro families, including haematological and haemoglobin analysis, haemoglobin synthesis, and globin messenger-RNA assay, have defined two alpha-thalassaemia phenotypes which resemble the severe (alpha-thalassaemia 1) and mild (alpha-thalassaemia 2) forms of the disorder described in Orientals. Genetic analysis suggests that subjects with the alpha-thalassaemia-1 phenotype are homozygous for the alpha-thalassaemia-2 determinant. Restriction-endonuclease mapping shows that alpha-thalassaemia-2 results from the deletion of one of the linked pair of alpha-chain genes. Hence the genotypes of the alpha-thalassaemia heterozygotes and homozygotes in these families are -alpha/alpha alpha and -alpha/-alpha respectively. If these are the usual alpha-thalassaemia genotypes in Negroes, these findings explain the difference in clinical expression of the disorder between Orientals and Negroes--in particular, the absence of haemoglobin Bart's hydrops and the rarity of haemoglobin-H disease in Negroes.
D044383:Black People; D002872:Chromosome Deletion; D002902:Chromosomes, Human, 16-18; D004262:DNA Restriction Enzymes; D005260:Female; D005796:Genes; D005914:Globins / Q000096:biosynthesis / Q000235:genetics*; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008297:Male; D010375:Pedigree; D010641:Phenotype; D012333:RNA, Messenger / Q000096:biosynthesis; D013789:Thalassemia / Q000235:genetics*
D012333:RNA, Messenger; D005914:Globins; D004262:DNA Restriction Enzymes