Arrange the following steps of PCR in correct sequence.
(A) Temperature induced denaturation of double stranded DNA.
(B) Isolation of gene of interest
(C) Amplification of gene by using Taq polymerase
(D) Primer annealing on the separated templates
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (B), (A), (D), (C)
(B) Isolation of gene of interest — first. The DNA to be amplified is taken out.
(A) Temperature induced denaturation of double stranded DNA. — second. Heat separates the two strands.
(D) Primer annealing on the separated templates — third. Primers bind to their matching sequences.
(C) Amplification of gene by using Taq polymerase — last. The thermostable enzyme extends the primers; repeated cycles make about a billion copies.
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.”