PCR stands for Polymerase Chain Reaction. In this reaction, gene (segment of DNA) of interest is synthesized in vitro and multiple copies are generated. The main steps of PCR- Denaturation - where the double-stranded template DNA is heated to separate it into two single strands. Annealing - where the temperature is lowered to enable the DNA primers to attach to the template DNA. Extension - where the temperature is raised and the new strand of DNA is made by the Taq polymerase enzyme.