beta 0 thalassemia, a nonsense mutation in man.

We determined the complete nucleotide sequence of the 5' noncoding region and the first 74 amino acids of the nonfunctional beta-globin mRNA in a patient with homozygous beta 0 thalassemia. We identified the molecular defect as a single nucleotide substitution in the coding region of the mRNA. At the position corresponding to amino acid 17, replacement of an adenine by a uracil changes the triplet AAG, which codes for lysine in the normal beta chain, to an amber termination codon, UAG. This type of beta 0 thalassemia represents an example of a nonsense mutation in man.