Covid-19 is a global pandemic caused due to a virus known as SARS-CoV-2. This disease is impacting the world to the extent that is not imagined by any of us. The key behind controlling the havoc caused by the disease is its early detection and treatment. The most reliable tool for detecting a viral infection is the RT-PCR test. The RT-PCR stands for Reverse Transcriptase- Polymerase Chain Reaction. For the time being, let us focus on the term PCR, i.e., Polymerase Chain Reaction; as the name suggests, it is a chain reaction that can amplify DNA exponentially. The enzyme involved in amplification is known as DNA polymerase hence the name Polymerase Chain Reaction. The reaction uses small strands of DNA known as primers that bind to the single stranded DNA by complementary base pairing of hydrogen bases. Further amplification of DNA is carried out by enzyme DNA polymerase by a principle known as ‘Thermal Cycling’. The reaction is carried out in a machine known as ‘Thermal Cycler’ capable of cycling the temperature at different values.
However, how exactly the virus is detected by DNA amplification? That is where the term ‘Reverse Transcriptase’ becomes significant. The SARS-CoV-2 virus has RNA as genetic material. However, RNA cannot directly be used for the amplification process in PCR; hence it is extracted from patient samples and is first converted to DNA by a process called ‘reverse transcription’ with the help of enzyme ‘reverse transcriptase’. DNA thus formed is used to detect the virus by using primers specific for viral genes in PCR.
