DNA amplification by the polymerase chain reaction.

The polymerase chain reaction (PCR) is a technique involving enzymatic amplification of nucleic acid sequences via repeated cycles of denaturation, oligonucleotide annealing, and DNA polymerase extension. PCR has revolutionized the practice of DNA technology as it allows virtually any nucleic acid sequence to be readily generated in vitro in relatively great abundance, so that subsequent analyses are not confounded by the presence of other DNA fragments or a lack of material with which to work. PCR also enables the sequence of individual DNA fragments to be altered. The method has advantages over conventional procedures for DNA cloning and analysis in many circumstances because it is faster, simpler, and more flexible. The total range and number of applications that have evolved in the short time since the first report of PCR are enormous. This review describes some of the history of PCR, the principle of the method, practical considerations for performing PCR, and a variety of applications.