Question

Brief about PCR.

Answer 1

PCR:

1. The technique of PCR is developed by an American biochemist named Kary Mullis in the year 1983.
2. Polymerase Chain Reaction or PCR is a technique in which a segment of DNA can be amplified several times. It is widely used in forensics, diagnosis of genetic disorders, cloning, etc.
3. PCR comprises three major steps- denaturation, annealing, and elongation.
4. In denaturation, the reaction mixture is heated at 94℃. At this temperature, the hydrogen bonds present between the two DNA strands are broken down, resulting in the formation of single-stranded DNA. The single-strand DNA now serves as a template for producing new DNA strands.
5. During the annealing step, the temperature is lowered to 54-60℃. The primers bind to the complementary sequences present on the template DNA. Primers are about 20-30 base long, single-stranded DNA or RNA sequences.
6. In the elongation step, the temperature is increased to 72℃. An enzyme called Taq polymerase attaches to the primer and carries out DNA synthesis in the 5’ to 3’ direction. As a result, a double-stranded DNA molecule is produced.