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What is PCR? | Polymerase Chain Reaction Explained

What is PCR? | Polymerase Chain Reaction Explained

What is PCR?

Polymerase chain reaction is a technique through which the DNA is ampified and desired copies of the DNA is extracted.

What’s with the name?

Polymerase stands for enzyme, chain means the type of reaction. PCR is a chain reaction. Therefore, it is an Enzyme linked chain reaction, which makes copies of the DNA.

PCR – Uses

This technique is used to diagnose infections, above all to detect viral infections.

For instance, The blood sample of the patient is taken and the viral DNA is extracted and amplified.

Used in crime investigation, as it involves DNA. Also, in branches of Biotechnology, Forensic and molecular biology.

Used in Genetic research

Materials required in PCR

Now, you have understood what is pcr and it’s uses. To run a reaction ingredients are required, so here are the ingredients or materials required for the PCR:

1) Thermal cycler or PCR machine

To understand the PCR, first of all it is necessary to understand what is PCR machine. PCR machine or thermal cycler machine is where the reaction takes place. Above all, it is the main machinery in which the DNA copies are made.

what is pcr

Contains small tubes to which the ingredients mentioned below are added.

2) Taq polymerase

The DNA polymerase used here in PCR, it is extracted from a bacteria called Thermus aquaticus which can withstand high temperature. Similarly, this enzyme too can withstand high temperatures.

It is ideal for PCR, because Taq polymerase is active around 70 degree celsius. Also, it is very heat stable.

what is pcr

3) Primers

Primers are short sequence nucleotides. It provides a starting point to initiate the reactions. Moreover, it helps to choose an exact well defined portion to amplify.

3) Nucleotides

These are the basic units of DNA. Required here to make copies with the denatured parts of the DNA.

4) DNA template

This is the original segment of DNA we want to amplify, the target DNA. To clarify, the amplification starts in this template.

Now, we are set with the ingredients. In addition, we are left to initiate the reaction.

what is pcr

The process of PCR is split into three parts:

Denaturation, Annealing and Extension

Here, is the explanation step by step:


The first step in PCR in which the temperature raised to 96 degree celsius. In other words, done to seperate the strands of the original DNA template. That is, one DNA template into two. Here, we will get two separate strands of the DNA.


In this second step, the machine temperature is reduced to 55 degree celsius.

After that, it results in the primer attachment to the target sequence of the stranded DNA or denatured DNA,


The last step in which the free nucleotides are required.

The temperature is increased to 72 degree celsius, meanwhile , it results in the activation of Taq polymerase. It will extend the primers to make new DNA strands.

These are the steps and the reaction occurs like a chain in which from one DNA we get two copies, further from two we get Four copies and so on, so for 100 reactions it can produce billions of copies.