Question

Which of the following is wrongly matched between column I and column II, with respect to Polymerase Chain Reaction (PCR)?

Column I	Column II
1. Primer	Oligonucleotide
2. Template	Double-stranded DNA
3. Polymerase	Taq polymerase
4. Synthesis	5’ to 3’ direction

• A. 1 only
• B. 1 and 3 only
• C. 2 only
• D. 2 and 4 only

Answer 1

The correct option is C 2 only

The synthesis of new strands in PCR is based on the nucleotide sequence of the template DNA. First, the double-stranded DNA is denatured into two single strands with the help of heat, which then act as a template individually. The primers bind to each of the single-stranded templates to initiate the process of replication. Double-stranded DNA does not directly act as a template in its entangled form, it acts as a template only when denatured.
Primers are small, chemically synthesised oligonucleotide sequences that are complementary to the base sequence present in the 3’ end of the template DNA and allow the replication in a selective manner.
DNA Polymerase facilitates and performs the incorporation of correct complementary nucleotide bases in the newly growing strand of the DNA by reading the template DNA. A purified and cloned DNA polymerase- Taq DNA polymerase, isolated from a thermophilic bacterium Thermus aquaticus, is the most commonly used polymerase enzyme in PCR. This DNA polymerase has a significant characteristic to withstand high temperatures upto $100°C$ and the enzyme finds its temperature of comfort at $72°C$ to perform its polymerase activity. The polymerisation by the DNA polymerase occurs in 5’-3’ direction by reading the template in 3’-5’ direction.