Abstract
The complete nucleotide sequence of the 5'' noncoding region and the first 74 amino acids of the nonfunctional .beta.-globin mRNA was determined in a patient with homozygous .beta.0 thalassemia. The molecular defect was identified as a single nucleotide substitution in the coding region of the mRNA. At the position corresponding to amino acid 17, replacement of an adenine [A] by a uracil [U] 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.