β-Thalassemia due to a deletion of the nucleotide which is substituted in the β(s)-globin gene

Sickle-cell anemia results from an A → T transversion in the second nucleotide of codon 6 of the β-globin gene. We now report an uncommon β-thalassemia gene that contains a deletion of this nucleotide. Thus, one mutation (GAG ← GTG) produces sickle-cell anemia, while the other (GAG ← GG) eliminates β-globin production. These data establish that different alterations affecting one specific nucleotide can produce either an abnormal hemoglobin or β-thalassemia. Moreover, the nucleotide sequence comprising codons 6-8 of the β-globin gene appears to be particularly susceptible to mutations affecting nucleotide number.