Screening for N-ras codon 61 mutations by mismatch PCR-RFLP.

MscI restriction enzyme digests of PCR-DNA resolved on 3% metaphor agarose gel containing ethidium bromide. PCR products harboring codon 61 of the N-ras gene were generated by nested PCR of CD138⁺-enriched cell lysate DNA. The mutant allele is resistant to enzyme digest. (A) Pre-enrichment: lane 1, uncut PCR-DNA; lane 2, HL60 DNA-positive control; lanes 3 to 7, representative patient samples; lane 8, normal DNA. (B) After-enrichment PCR: lane 1, an aliquot of the enzyme digest product of HL60 PCR-DNA from panel A; lane 2, HL60 PCR-DNA showing enrichment of the mutant allele; lanes 3 to 7, patient samples; lane 8, normal DNA.