Question

Amplification of gene of interest by using PCR may go up to

• A. $1.0$ trillion times
• B. $1.0$ million times
• C. $1.0$ billion times
• D. $0.1$ million times

Answer 1

The correct option is C $1.0$ billion times

Polymerase chain reaction or PCR is a reaction carried in vitro to amplify a specific DNA sequence or gene of interest and create its multiple copies.

Steps involved in PCR are as follows:

• Denaturation - In this step separation of the two strands of double stranded DNA done by application of heat at $94-{95}^{\circ }C$.
• Annealing - This step involves the hybridisation of the primers with specific sequences of each of the strands of the template DNA. Primers are small oligonucleotides up to $18-24$ nucleotides long synthesised chemically. This process is carried out at $50-{56}^{\circ }C$.
• Extension - In this step the Taq DNA polymerase synthesises DNA by adding dNTPs (deoxyribonucleotides) to the free ends of the primers. The extension of DNA is carried out at ${72}^{\circ }C$. This helps in synthesising complementary strands.

In PCR, a region of DNA is amplified multiple times, approximately one billion times a DNA can be multiplied using thermostable DNA polymerase.