RT PCR

Disclaimer: Copyright infringement not intended.

Context

• India reported 18,819 new Covid-19 cases and 39 deaths in the last 24 hours. With rising Covid-19 cases in India, states have been asked to screen 2% of the international passengers coming to India at random and send all positive samples for genome sequencing.

RT-PCR

• The real-time polymerase chain reaction (RT-PCR) test is the most commonly used one for Covid-19. It is primarily based on PCR, a process that repeatedly copies and amplifies the specific genetic fragments of the virus, ensuring that there is enough of a sample to conduct the analysis.
• The RT-PCR test starts with a simple swab taken from inside a person’s throat or nose. Coronaviruses have RNA or ribonucleic acid as their genetic material. However, swabs from patients yield only a tiny quantity of RNA, which is not adequate for the testing process.
• To overcome this problem, the RNA — a single-strand molecule — is converted into a two-strand DNA using an enzyme. This is known as reverse transcription.
• Researchers select specific areas in the genome that do not mutate rapidly as the virus evolves, and create copies of these using the PCR process.
• The next step is the use of primers. These are small pieces of DNA designed only to bind to the selected DNA sequence of the SARS-CoV-2’s viral genome. Along with primers, the process uses a fluorescent dye, which acts as the probe.
• The patient sample, primer and probe are together left in the PCR machine for the binding process to take place. A fluorescent signal marks the presence of the virus.
• The time duration for the testing process is around four to eight hours.

https://indianexpress.com/article/lifestyle/health/coronavirus-india-live-news-updates-covid-count-deaths-delhi-mumbai-bangalore-chennai-cases-7997400/