Question

Which of the following is not correct for a successful PCR?

• A. Thermostable DNA polymerase
• B. Nanogram of DNA template
• C. Primer with exposed 5'−OH group only
• D. dNTPs

Answer 1

The correct option is C Primer with exposed 5'−OH group only

Polymerase chain reaction (PCR) is a technique to make many copies of a specific DNA region in vitro.

PCR uses a thermostable DNA polymerase, Taq polymerase, and requires DNA primers designed specifically for the DNA region of interest.

1. DNA polymerase is very heat-stable and is most active around 70°C. This heat-stability or thermostability makes Taq polymerase ideal for PCR.

2. Nanogram of DNA template is required so that primers bind to opposite strands of the template DNA, just at the edges of the region to be copied. The primers bind to the template by complementary base pairing.

3. PCR primers are short pieces of single-stranded DNA. In the annealing step, two primer DNA are attached at 3' end of single-stranded DNA or has exposed 3'−OH group only.

4. Deoxyribonucleoside triphosphates (dNTPs) acts as a substrate and provides energy for a polymerization chain reaction.

So, primer with exposed 5'−OH group only is not correct for a successful PCR.