The Polymerase Chain Reaction (PCR) was invented in 1983 by the biochemist Kary Mullis and has since become a fundamental part of many procedures used in genetic testing.
PCR is an amplification technique, the use of which enables millions (or even billions) of copies of a specific DNA sample to be created. These copies may be of the entire DNA sample, or a specific sequence of interest. Amplification is important as it allows scientists to take a small DNA sample and amplify it to a large enough amount to study in detail. Without amplification DNA testing on many samples would not be possible.
PCR methods rely on thermal cycling, which is the exposure of samples to repeated cycles of heating and cooling to permit temperature dependent, enzyme driven reactions. For each of these “temperature cycles”, the double stranded DNA is opened up creating 2 single stranded DNA sequences in a part of the process known as “denaturation”. These single stranded DNA sequences are then both converted to double stranded DNA sequences in a part of the process known as “elongation”. The end result is that the total number of DNA strands is doubled with each cycle. As PCR comprises of multiple cycles, this technique allows for a huge amplification of the amount of DNA available to be tested.
Which DNA sequences are amplified depends on the primers used during PCR. Primers are complimentary short sequences that bind to the single stranded DNA sequences and start the process of elongation. These can either be universal, meaning that PCR amplifies an entire DNA sample, or targeted, meaning that they amplify a specific sequence of interest.
Yourgene Health PCR based kits fall into 2 different categories dependent on which method of PCR they use. Both methods rely on the detection or lack of detection of a sequence of interest after amplification to show the presence or absence of said sequence.