Question

Polymerase chain reaction employs

• A. Primers and DNA ligase
• B. DNA ligase only
• C. DNA polymerase only
• D. Primers and DNA polymerase

Answer 1

The correct option is D Primers and DNA polymerase

Polymerase chain reaction (PCR) is a technique used for the in vitro amplification of the DNA fragments or gene of interest to create multiple copies.

Tools in PCR include the following:

• Taq polymerase
• Deoxyribonucleotides
• Primers

Primers are small oligonucleotides up to $18-24$ nucleotides long synthesised chemically. They bind with specific sequences of each strand of the template DNA for amplification.

Taq polymerase is a thermostable enzyme that is used to catalyse the addition of dNTPs to the primer thus helping in the extension of the DNA strand. This process of extension is carried out at ${72}^{\circ }C$.

DNA ligase creates the phosphodiester bond between the nucleotides of DNA fragments and joins them together. It helps in the joining of vectors and DNA of interest in genetic engineering. DNA ligase has no role to play in PCR.

Hence the correct option is
d. Primers and DNA polymerase