What is polymerase chain reaction.?

Answer 1

Thepolymerase chain reaction (PCR) is a technique widely used in molecular Biology. It derives its name from one of its key components, a DNA polymerase used to amplify (i.e., replicate) a piece of DNA by in vitro enzymatic replication. As PCR progresses, the DNA thus generated is itself used as template for replication. This sets in motion a chain reaction in which the DNA template is exponentially amplified. With PCR it is possible to amplify a single or few copies of a piece of DNA across several orders of magnitude, generating millions or more copies of the DNA piece. PCR can be performed without restrictions on the form of DNA, and it can be extensively modified to perform a wide array of genetic manipulations.

The reaction is of much use in molecular diagnosis of a disease, where the causative organism can be identified and characterized up to strain level once multiple copies of DNA are obtained.

The reaction takes place in a step wise manner- Separation of the DNA strands, Primer Annealing followed by Duplication with each reaction carried out at different temperatures in the presence of a thermostable DNA polymerase enzyme.

The PCR is carried out in a Thermocycler - an instrument that enables temperature change at different stages for required time intervals which would be otherwise impractical meaning handling manually would not be possible without errors and contamination. Moreover this approach in diagonising a disease is faster compared to the usual methods of specimen collection, isolation, culturing and growth followed by identification.