Question

What does PCR stand for? Describe the different steps of PCR.

Answer 1

PCR stands for polymerase chain reaction. It is a process which is used to create copies of DNA fragment. In this, PCR reaction mixture contains Taq polymerase, primers, template DNA and nucleotides There are three steps of PCR namely, denaturation step, annealing step and extension step.

1. Denaturation step: In this step, the reaction is heated at 94${}^0$C in order to denature the DNA strands. This results in a single-stranded template.

2. Annealing step: In this step, the reaction is cooled down to 55${}^0$C to 65${}^0$C in order to bind primer to their complementary sequences on the single-stranded template DNA.

3. Extension: This is the last step of PCR process. In this step, the temperature of reaction is raised to 72${}^0$C so that Taq polymerase enzyme synthesizes new strands of DNA by extending primer.

This cycle repeats 25 to 35 times in the entire process.