The polymerase chain reaction: new variations on an old theme.

The polymerase chain reaction (PCR) is firmly established as the method of choice for DNA amplification, though alternative strategies, such as the ligase chain reaction, may also be employed. Despite the continued development of PCR applications for gene mapping and diagnostics, few revolutionary improvements have been made to the technique. The major exception is long-accurate PCR, which has increased the length of amplifiable DNA by an order of magnitude.