Two cloned β thalassemia genes are associated with amber mutations at codon 39

Two β globin genes from patients with the β⁺ thalassemia phenotype have been cloned and sequenced. A single nucleotide change from CAG to TAG (an amber mutation) at codon 39 is the only difference from normal in both genes analyzed. The results are consistent with the assumption that both patients are doubly heterozygous for β⁺ and β° thalassemia, and that we have isolated and analyzed the β° thalassemia gene.