GeneID: 3

Description:
The human alpha globin gene cluster located on chromosome 16 spans about 30 kb and includes seven loci: 5’-HBZ2-ΨHBZ1-ΨHBA2-ΨHBA1-HBA2-HBA1-θ-3’. The alpha-2 (HBA2) and alpha-1 (HBA1) coding sequences are identical. These genes differ slightly over the 5' untranslated region and the introns, but differ significantly over the 3' untranslated region. Two alpha chains plus two beta chains constitute HbA, which in normal adult life comprises about 97% of the total haemoglobin; alpha chains combine with delta chains to constitute HbA-2, which together with HbF (fetal haemoglobin) makes up the remaining 3% of adult haemoglobin. Alpha thalassaemias result from deletions of one or both of the HBA2 and HBA1 genes; some non-deletion alpha thalassaemias have also been reported. Three normal alpha genes give a silent carrier state. Two normal alpha genes result in microcytosis (so-called heterozygous alpha-thalassaemia). One normal alpha gene results in microcytosis and haemolysis. No normal alpha genes result in 'homozygous alpha-thalassaemia' manifested as fatal hydrops fetalis.

Synonyms: HBA-T2

Comments:
N/A

Number of entries/variants: 555

1. Liebhaber SA, Goossens MJ, Kan YW, Cloning and complete nucleotide sequence of human 5'-alpha-globin gene., Proc. Natl. Acad. Sci. U.S.A. , 77(12), 7054-8, 1980 PubMed
2. Higgs DR, Vickers MA, Wilkie AO, Pretorius IM, Jarman AP, Weatherall DJ, A review of the molecular genetics of the human alpha-globin gene cluster., Blood , 73(5), 1081-104, 1989 PubMed