Polymerase Chain Reaction

Polymerase Chain Reaction


PCR machine is laboratory apparatus which is used to amplify DNA segments through polymerase chain reaction (PCR). This machine maintains needed temperature and make millions of copies DNA segments by PCR.

Tubes containing reaction mixtures put into a thermal block in PCR machine. This machine then increases and decreases the blocks temperature in different steps.

Now, what is PCR (polymerase chain reaction). It is a procedure that is used in the lab to amplify particular section of DNA from small amount of DNA.

It was developed in 1983 by Kary Mullis and he got Nobel Prize for his pioneering work.

It is used in medical or biological or forensic research labs. It is used to process DNA for sequencing, to detect the presence or absence of a gene, to identify pathogens

Ingredients to set up PCR are: DNA template that is to be copied, primers, DNA to initiate PCR. DNA nucleotide bases used to construct the new strand of DNA. Taq polymerase enzyme is required to add in the newly synthesized DNA bases. Buffer to maintain right conditions for the reaction.

PCR process involves heating or cooling process called as thermal cycling and it occurs in PCR machine.

Three stages of PCR are:

1. Denaturing : Here, double-stranded template DNA is heated so that two separated into two single strands.

2. Annealing: In this step, temperature is lowered so that DNA primers attach to template DNA.

3. Extending: Temperature is now raised so that new strand of DNA is formed by enzyme Taq polymerase.

These steps repeated 20-40 times to double the number of copies of DNA each time.

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