Steps of Polymerase Chain Reaction (PCR) are given below. Arrange them in the correct sequence.
A. Annealing of primers to the template DNA
B. Isolation of gene of interest
C. Extension of primer end on the template DNA using Taq polymerase
D. Denaturation of template DNA by heating
Choose the correct answer from the options given below.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → B, D, A, C
B. Isolation of gene of interest — first. The DNA to be copied is obtained.
D. Denaturation of template DNA by heating — second. The two strands separate.
A. Annealing of primers to the template DNA — third. Primers bind to their matching sequences.
C. Extension of primer end on the template DNA using Taq polymerase — last. The thermostable enzyme adds nucleotides to the primers.
NCERT Extract:
Amplification of Gene of Interest Using PCR – “PCR stands for Polymerase Chain Reaction. In this reaction, multiple copies of the gene (or DNA) of interest is synthesised in vitro using two sets of primers (small chemically synthesised oligonucleotides that are complementary to the regions of DNA) and the enzyme DNA polymerase. The enzyme extends the primers using the nucleotides provided in the reaction and the genomic DNA as template. If the process of replication of DNA is repeated many times, the segment of DNA can be amplified to approximately billion times, i.e., 1 billion copies are made. Such repeated amplification is achieved by the use of a thermostable DNA polymerase (isolated from a bacterium, Thermus aquaticus), which remain active during the high temperature induced denaturation of double stranded DNA.”