Thermostable DNA polymerase enzyme is extracted from Thermus aquaticus. Polymerase chain reaction is the process of making multiple copies of the DNA segment in vitro. The double stranded is denatured by using high temperature. DNA polymerase is used to add nucleotides on the DNA strand. High temperature inactivate the DNA polymerase. Taq polymerase can withstand the high temperature used for the denaturation and separation of DNA.