Polymerase chain reaction (PCR)

PCR stands for polymerase chain reaction; it is a laboratory technique used to amplify DNA sequences.

It is used in many fields, including forensics, medicine, and molecular biology
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Polymerase chain reaction was invented by Kary Mullis in 1983.

The main components of PCR include DNA polymerase, primers, nucleotides, and a buffer system.

This PCR technique involves three steps: denaturation, annealing, and extension.

Denaturation: The first step in PCR, denaturation, is required to separate the double-stranded DNA sample.

Denaturation leads to the formation of single strands of DNA by breaking hydrogen bonds present between base pairs. It is done at 94-98°C for 20-30 seconds.

Annealing: The second step in PCR, annealing of the primer, the reaction temperature is lowered up to 55°C to allow complementary single strands of DNA template.

A proper temperature needs to be maintained in order to allow highly specific and proper primer hybridization.

Then DNA polymerase binds to the template-primer hybrid and starts the DNA synthesis.

Extension: A thermostable DNA polymerase is used for this purpose; Taq polymerase is commonly used for this purpose.

The DNA polymerase adds nucleotides in 5′-3′ directions and synthesizes the complementary strands of the DNA template; it is done at 75-80°C (72°C).

These three steps of the PCR cycle were repeated 25-30 times, and with this DNA sample, it can be amplified a billion times.

Gel electrophoresis is used to visualize the result of polymerase chain reaction.