Analysis of enzymatically amplified β-globin and HLA-DQα DNA with allele-specific oligonucleotide probes

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Abstract
Allelic sequence variation has been analysed by synthetic oligonucleotide hybridization probes which can detect single base substitutions in human genomic DNA1–3. An allele-specific oligonucleotide (ASO) will only anneal to sequences that match it perfectly, a single mismatch being sufficient to prevent hybridization under appropriate conditions4. To improve the sensitivity, specificity and simplicity of this approach, we used the polymerase chain reaction (PCR) procedure5 to enzymatically amplify a specific segment of the β-globin or HLA-DQα gene in human genomic DNA before hybridization with ASOs. This in vitro amplification method, which produces a >105-fold increase in the amount of target sequence, permits the analysis of allelic variation with as little as 1 ng of genomic DNA and the use of a simple ‘dot blot’ for probe hybridization. As a further simplification, PCR amplification has been performed directly on crude cell lysates, eliminating the need for DNA purification.