Single Specific Primer-Polymerase Chain Reaction (SSP-PCR) and Genome Walking

The polymerase chain reaction (PCR) is used for selective amplification of DNA fragments from both prokaryotes and eukaryotes (1–3). The only requirement for amplification is that the sequence of the extremities of the DNA fragment to be amplified be known (4 ). This places a limitation on the use of PCR in the amplification of adjacent unknown regions. We have developed a method that allows the amplification of double-stranded DNA even when the sequence information is available at one end only (5 ). This method, the single specific primer-PCR (SSP-PCR), permits amplification of genes for which only a partial sequence information is available, and allows unidirectional genome walking from known into unknown regions of the chromosome.