Question

Match each step in a PCR cycle to its description.

Unwind DNA to expose single strands	A. Extension
Temperature drop that allows primers to hybridize with the template	B. Heat based denaturation
Temperature increase that enables Taq to become maximally active	C. Annealing

Answer 1

1. Unwind DNA to expose single strands- Heat based denaturation
2. Temperature drop that allows primers to hybridize with the template- Annealing
3. Temperature increase that enables Taq to become maximally active- Extension

The PCR technique was developed by Kary B Mullis in 1981. This technique is used for multiplication of recombinant DNA several thousand times (109 folds) in few hours. It has major three steps:

1. Denaturation
2. Annealing
3. Extension

1. Denaturation- Carried out at a temperature of more than 95o C. In this process, the double-stranded target DNA gets denatured i.e. the cleaving of H-bond takes place, thus converting double-stranded (ds) DNA into single-stranded (ss), that will act as a template for next round of DNA synthesis.

2. Annealing- Takes place at a temperature of nearly 55o C. At this temperature, hybridization between primer and template DNA

3. Extension- The temperature required is above 70 o C. It is an enzymatic process and takes place in the presence of Taq DNA polymerase (because of its thermostable nature at 94o C), that synthesise DNA.

These steps are repeated many times for bulk amplification of target DNA.

Wriginal target duplemy ONA - Denaturation to at 95°C. I 2 separation of dsDNA Dintio SSDNA that acts as template - - g' primers - TT ve Annealing 6 - 3 Synthetic primer Panneals to complementary segment on a each strand & I extension by DNA polymerase - dNTPs d entension by V Tag DNA polymer were: W