HSC Science (General) 12th Board ExamMaharashtra State Board
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Describe the Steps of PCR Technique. - HSC Science (General) 12th Board Exam - Biology

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Question

Describe the steps of PCR technique.

Solution 1

One cycle of Polymerase Chain Reaction involves three basic steps:
a. Denaturation b. Annealing c. Polymerization

a. Denaturation:
The desired DNA is heated to a high temperature of about 91°C and forms a single stranded DNA. It results in the separation of the two strands of DNA, each of which would function as a template for the synthesis of a new molecule of DNA.

b. Annealing:
1. It is the process in which the two primers (oligonucleotides) hybridise to each of the strands of DNA. It requires a temperature of 55°C.

c. Polymerization:
In this step, the Taq polymerase carries out the synthesis of DNA region between the two primers by using deoxyribonucleotides (dNTPs) and Mg2+. The optimum temperature for this polymerization reaction is 72°C.

Solution 2

The three essential steps of PCR technique are -

1) Heat denaturation: This step involves heating of DNA at about 91°C. The heating breaks the hydrogen bonds to make ssDNA. The DNA molecule with more G-C pairs needs the higher temperature.

2) Annealing: It is pairing of primers to the ssDNA segment. The primers have to be designed as per the requirement. This step requires temperature at about 55°C

3) Polymerisation: The temperature is raised to 72°C. The Taq polymerase adds dNTPs behind the primer on the ssDNA. These three steps constitute one cycle of the reaction (3-5 mins). The process is carried out for about 28-30 cycles beyond which its reliability decreases.

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 2014-2015 (October) (with solutions)
Question 3.1.1 | 3.00 marks
 2017-2018 (March) (with solutions)
Question 3.1.2 | 2.00 marks
Solution Describe the Steps of PCR Technique. Concept: Gene Amplification (PCR).
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