Polymerase Chain Reaction

PCR is an in vitro method for amplifying a selected DNA sequence that does not rely on the biologic (in vivo) cloning method . PCR permits the synthesis of millions of copies of a specific nucleotide sequence in a few hours. It can amplify the sequence, even when the targeted sequence makes up less than one part in a million of the total initial sample. The method can be used to amplify DNA sequences from any source, including viral, bacterial, plant, or animal. The steps in PCR are summarized in Figures 1 and 2.

Figure 1: Steps (denature, anneal, extend) in one cycle of the polymerase chain reaction.

Figure 2:  Multiple cycles of the polymerase chain reaction.