Question

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

Answer 1

PCR stands for polymerase chain reaction, which is helpful to produce millions of copies of specific DNA from a single sample, sometimes it is helpful to produce single copy also, and it is a very crucial process in genetic technology.

Complete answer:
Polymerase chain reaction was developed in the year 1983 by the scientist Karry Mullis for which he was awarded Noble prize.

PCR technology is mainly used for amplification of the specific required DNA.
In this technique millions of copies of DNA are produced from the small sample.
It is used in the research lab for the sequencing and to identify the gene for pathology in case of infections and also in case of forensic cases to produce more copies from the given samples.
For the PCR technology some ingredients are required, which includes.
1. Sample DNA or DNA template which is to be copied.
2. Primers which are helpful for the binding and to initiate the process of PCR technique.
3. In order to construct the new strands, it requires some DNA nucleotide bases.
4. Polymerase enzyme.
5. Buffer is required to establish the perfect environment.
Steps of PCR
Denaturing : In this step the double standard template is heated in order to separate them into single strands.
Because of heating the hydrogen bonds which are present between the strands break as they are weak bonds.
Annealing : In this step the temperature is lowered so that primers will attach to the templates of the DNA strands.
Extension : In this step the temperature is raised so that new strands of DNA are made by the polymerase enzyme.
All these steps are repeated 20 to 40 times each time, which helps in doubling the number of copies of the DNA strands.

Note: In denaturing stage the temperature required is 92 to 95 degree Celsius for 15 to 30 sec, whereas in annealing stage the temperature required is 55 to 60 degree Celsius around 20 to 30 sec, in extending stage the temperature is raised to 72 degree Celsius. It is the ideal or optimum temperature for Taq polymerase enzyme.