Question

Describe polymerase chain reaction (PCR). How did we utilize this technique in lab?

Answer 1

Polymerase chain reaction (PCR) is an in-vitro DNA amplification technique that is based on the ability of the DNA polymerases to make the new complementary strands of the template DNA and hence, increasing the number of copies of the available DNA. The components of PCR include:

1. A DNA template strand (which will be amplified)

2. A thermostable DNA polymerase (such as Taq polymerase)

3. DNA primers

4. Di-Deoxynucleotide triphosphates (ddNTPs)

The steps of a PCR are as follows:

1. Denaturation: In this step, the double-stranded template DNA is separated into individual single strands. This is done by heating the strands at high temperatures (90oC).

2. Annealing: This step involves the annealing of the DNA primers to the complementary sequence of the single-stranded DNA. The annealing takes place after cooling the reaction mixture at 55-65oC.

3. Extension: The next step is the addition of the complementary nucleotides by the DNA polymerase. This step takes place at 72oC.

This completes a single cycle of a PCR. The number of cycles repeated depends upon the length of the template strand and the number of copies needed. The PCR can make up to billion of copies of the DNA template. Each cycle of PCR increases the copies of the DNA exponentially.