Read the given paragraph and answer the question:

The step 'B' in the figure is called as:

Annealing

The correct answer is Option (3) -Annealing

The PCR involves three major cyclic reactions:

Denaturation

Annealing

Elongation

Each cycle of polymerase chain reaction has three steps. They are:

1. Denaturation: The first step in PCR is denaturation. Denaturation is required to separate the double-stranded DNA sample. It is done at 94-98 ℃ for 20-30 seconds. It breaks the hydrogen bonds present between base pairs. Denaturation leads to the formation of single strands of DNA.
2. Annealing: The second step is the annealing of the primer. Here the reaction temperature is lowered to allow the complementary base pairing between the primer and the complementary part of the single strands of the DNA template. A proper temperature needs to be maintained in order to allow highly specific and proper primer hybridisation. Then DNA polymerase binds to the template-primer hybrid and starts the DNA synthesis.
3. Extension: A thermostable DNA polymerase is used for this purpose. Taq polymerase is commonly used for this purpose. It is done at a temperature of 75-80 ℃ (72℃). The DNA polymerase adds nucleotides in the 5’-3’ direction and synthesises the complementary strand of the DNA template.

Polymerase chain reaction (PCR) : Each cycle has three steps: (i) Denaturation; (ii) Primer annealing; and (iii) Extension of primers