The term PCR stands for Polymerase chain reaction. It is used in molecular biology to make the copies in a small sections of DNA. By using the PCR it is possible to generate miillions of same copies at a particular section of the DNA and it is a very common tool in medical and biological research labs. PCR is needed because the components required for DNA sample, primers, free nucleotides called ddNtps and DNA polymerase.
Almost all PCR applications emphasis a heat- stable DNA polymerase. If the polymerase heat than the high temperature of denaturation occur before the use of taq polymerase which is the DNA polymerase cycle. The PCR works when DNA is copied in a cell devision but it is carried out with a controlled manner in a laboratory.