Describe the steps of PCR technique. - Biology

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Short Note

Describe the steps of PCR technique.

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Solution 1

One cycle of Polymerase Chain Reaction involves three basic steps:

  1. Denaturation
  2. Annealing
  3. Polymerization

1. 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.

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

3. Polymerization:
In this step, the Taq polymerase carries out the synthesis of the 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 the PCR technique are:

1. Heat denaturation: This step involves the 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 a higher temperature.

2. Annealing: It is the 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.

Concept: Commercial Applications of Biotechnology
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2014-2015 (October)

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