Question

The correct order of steps in Polymerase Chain Reaction (PCR) is
(1) Extension, Denaturation, Annealing
(2) Annealing, Extension, Denaturation
(3) Denaturation, Extension, Annealing
(4) Denaturation, Annealing, Extension

Answer 1

Correct Option(4) Denaturation, Annealing, Extension

Explanation:

The Polymerase Chain Reaction (PCR) involves three basic steps; denaturation, annealing, and extension. In the denaturation step, DNA is heated at high temperature (94°C to 96°C) to separate the two strands. In the next step (annealing) the two oligo-nucleotide primers anneal to each single-stranded template DNA. This step is carried out at a lower temperature (40°C to 60°C). The final step is an extension, wherein Taq DNA polymerase synthesises the DNA region between the primers, using dNTPs (deoxynucleoside triphosphates) and Mg²⁺ ions.

Polymerase Chain Reaction (PCR): Each cycle has three steps ;

(i) Denaturation; (ii) Primer annealing; and (iii) Extension of primers