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Rapid detection of the hemoglobin C mutation by allele-specific polymerase chain reaction.

One of every 625 black couples in the United States is at risk for having a child with hemoglobin SC disease. Prenatal diagnosis for the sickle cell mutation is possible within a few hours (Chehab et al. 1987). The region around the sickle cell mutation is amplified by polymerase chain reaction (PCR) and is digested by a restriction endonuclease whose recognition site is abolished by the A-to-T mutation at codon 6 in the sickle gene, and the resulting abnormal fragment is detected with ethidium bromide staining after electrophoresis. Detection of the G-to-A mutation at codon 6 in the hemoglobin C gene however is more difficultsince no known restriction-endonuclease site is abolished or created by the mutation-and usually requires allelespecific oligonucleotide hybridization (Studencki et al. 1985). Allele-specific amplification by PCR with primers, the 3' ends of which are placed at the mutation site, has been shown to be possible in some instances (Okayama et al. 1989; Wu et al. 1989), while in other instances the amplification efficiency is not impaired by terminal 3' nucleotide mismatches (Kwok et al. 1990). We describe here a rapid allele-specific PCR amplification technique that allows detection of the hemoglobin C mutation in an even shorter time span than the one required for detection of the hemoglobin S mutation.