Polymerase Chain Reaction, or PCR Applications.

PCR Applications

Polymerase Chain Reaction, or PCR, is a procedure that was invented in the late 1980’s and is widely used in the selective amplification of a chosen region of a DNA molecule. This chosen region can be from any part of the DNA molecule, however PCR will only work if the base sequences of the 3’ and 5’ ends are known. This is to ensure that two short oligonucleotides, acting as primers, can anneal onto the DNA strands and initiate DNA synthesis reactions.

The process of PCR is dependant on the thermostable DNA pol I enzyme from the bacterium Thermus aquaticus The basic procedure of PCR is several cycles of denaturation, hybridisation and synthesis resulting in the eventual synthesis of several hundred million copies of the amplified DNA fragment (see Fig.1 for the overall stages of PCR).

Following its completion, a sample of the mixture is analysed by agarose gel electrophoresis, where it is visible as a discrete band by staining with Ethidium Bromide.

Fig.1 Summary of PCR

PCR is a very sensitive technique and because of this it is used worldwide in molecular biology. There are many applications of PCR, all of which have aided the current knowledge into DNA sequencing and cloning.

PCR is frequently used when screening gene libraries after standard cloning experiments. This method can identify and isolate a clone carrying a particular region of the genome from the thousands of similar clones that contribute a gene bank. In this case PCR is known as ‘in vitro amplification’ as it utilises two oligonucleotide primers that flank the regions ...