A novel δ° arising from a frameshift insertion, detected by direct sequencing of enzymatically amplified DNA

Abstract
We describe a novel mutation in the δ globin gene of a compound heterozygote for δ° thalassemia and a deletion type Gγ+(Aγδβ)° thalassemia. The δ gene was amplified using the polymerase chain reaction (PCR), and the amplified material was used in a direct sequencing experiment. The nucleotide sequence of the mutant δ gene showed that the insertion of an extra nucleotide at the third position of codon 91 in the second exon, which gives rise to a premature stop codon at position 94, leads to the silencing of this gene. The presence of the mutation in the carriers of δ-thalassemia in this family was confirmed by dot blot hybridization. A possible model for the insertion of the extra nucleotide is discussed.