Molecular biology techniques allow the detection of minute amounts of nucleic acids (DNA, RNA) in a biological specimen. These techniques are used today in humans to detect micro-organisms, look for genetic mutations associated with certain diseases and cancers, perform paternity tests, practise forensic medicine, establish family trees, etc.
The principle behind all of these techniques consists first of multiplying the amount of DNA of interest in a specimen thousands if not millions of times in order to analyze it later using various methods (colorimetry, sequencing, etc.). The amplification of nucleic acids requires naturally occurring enzymes (proteins) whose role is to closely or remotely assist with cell multiplication. Simply stated, with each cell division, the DNA present in the chromosomes of the mother cell must be doubled with the help of certain enzymes in order to give birth to two independent daughter cells. One of the key enzymes in this process is called “DNA polymerase.” This repeatedly used enzyme is the basis of the PCR (polymerase chain reaction) technique. Some techniques use other enzymes to achieve the same amplification. These techniques are grouped under the more generic label of “nucleic acid amplification tes ts” (NAATs). In some cases, there is a need to amplify RNA (ribonucleic acid) rather than DNA (deoxyribonucleic acid). As its name suggests, DNA polymerase is capable of copying DNA (but not RNA). Before DNA polymerase can be used to amplify RNA, an initial copy of the RNA must first be made as complementary DNA using another enzyme called “reverse transcriptase.” This variant of PCR, known as “RT-PCR,” is the main technique used by laboratories to confirm the presence of SARS-Cov-2 responsible for the COVID-19 pandemic. SARS-CoV-2 is a virus containing only RNA.