Use of oligonucleotide hybridization in the characterization of a β(o)-thalassemia gene (β³⁷ TGG→TGA) in a Saudi Arabian family

Analysis of restriction site polymorphisms in the β-globin gene cluster of a Saudi Arabian female with β(o)-thalassemia demonstrated that both of her β-globin genes were missing a nonpolymorphic AvaII site in exon 2. Examination of the normal nucleotide sequence surrounding this AvaII site revealed that either of two nucleotide substitutions, TGG→TAG or TGG→TGA, could produce a nonsense codon at condon 37 and eliminate the AvaII site. Consequently, two oligonucleotides (19-mers spanning codons 36 through 41 and containing either TAG or TGA at codon 37) were synthesized and hybridized against genomic DNA of the proband and her family. Specific hybridization with one of the oligomers demonstrated that the patient's β(o)-thalassemia was the result of homozygosity for the TGG→TGA mutation at codon 37. In certain cases, oligonucleotide hybridization using genomic DNA may obviate the need for gene cloning and sequencing in the characterization of point mutations.