Polymerase Chain Reaction (PCR) may be a technical term and on the face of it sound like a subject you might not be familiar with. However, I’m sure everyone’s either watched CSI or a cheesy American-type chat show where several women go on the show to take a paternity test. Well, put simply, PCR is the process of getting those results. It is actually the process of testing DNA in different conditions to get a certain outcome i.e. to find out if two DNA samples match.
Developed in 1983 by Nobel Prize winning Kary Mullis, he applied his knowledge in biochemistry to improve PCR testing techniques and after years of research the work finally paid off.
Polymerase chain reactions are now used in many areas of science and healthcare. A few of its uses include DNA cloning for sequencing, functional analysis of genes, the diagnosis of hereditary diseases, the detection and diagnosis of infectious diseases and for identifying genetics in fingerprints (which is mainly used in forensic science and paternity testing).
For PCR to work the conditions have to be exacting for the outcome to be as precise as possible; this will include an optimum temperature being reached, which is normally around 70°C, a sample or DNA template which will be amplified for testing and two primers which are samples of the DNA being tested against the now amplified DNA sample.
PCR relies heavily on thermal cycling, which is a process of heating and cooling at a rapid speed. Thermal cycling has become one of the most popular applied processes currently in use and is used alongside many other techniques in all areas of science, not just biochemistry.
The process of PCR is commonly divided into three different stages which include the exponential amplification, the levelling off stage when the reaction slows and the plateau stage when no product is created because the reagent has been used.
In the optimisation stage the conditions at which PCR takes place are optimised. This needs to be done because of its sensitivity to contamination or giving spurious results. There are different types of procedures which have been developed to optimise PCR, these include spatial separation, addition of reagents and computer simulation.
Finding reliable and efficient PCR kits can be a problem however so specialist companies develop a range of these kits which are then shipped across the UK and the EU. As all the products have been developed by specialists they have passed certain quality control tests to make them suitable for use by many client sectors.
PCR, a simple stroke of genius that is now a necessity of science!
About the author: Grant Holdsworth wrote this article on DNA testing on behalf of www.primerdesign.co.uk.