Vet360 Vol 4 Issue 2 April 2017 Vet360 | Page 21

LABORATORY UNDERSTANDING PCR Remo Lobetti BVSc MMedVet (Med) PhD Dipl ECVIM (Internal Medicine) Bryanston Veterinary Hospital PO Box 67092, Bryanston, 2021, South Africa Email: [email protected] INTRODUCTION The polymerase chain reaction (PCR) is a technique in molecular biology that analyses short sequences of DNA or RNA and is used in the diagnosis of a variety of infectious and genetic diseases. PCR is used to amplify a piece of DNA resulting a chain reaction in which the target DNA is amplified exponentially leading to numerous copies of that DNA, which can then be easily visualised on an agarose gel. By use of a reverse transcriptase step, RNA is converted to DNA and thus the technique can also be used to detect RNA (RT-PCR). The key to understanding PCR is that every human, animal, plant, parasite, bacterium, or virus contains genetic material sequences (nucleotide sequences or pieces of DNA or RNA) that are unique to their species, and to the individual member of that species. Thus if a sample contains segments of DNA or RNA, PCR can amplify these unique sequences so they can then be used to determine with a very high probability the identity of the source (a specific person, animal, or pathogenic organism) of the trace DNA or RNA found in or on almost any sample of material. Once the amplification is done, the amplified segments are compared to other nucleotide segments from a known source (for example, a specific person, animal, or pathogenic organism), which is done by placing PCR- generated nucleotide sequences next to known nucleotide sequences in a separating gel. PCR IN PRACTICE PCR can detect and identify pathogenic organisms, especially those that are difficult to identify with other methods; diagnose genetic diseases; and identify and characterise genetic mutations found in certain cancers. Issue 02 | APRIL 2017 | 21