Question

The test for SARS-CoV-2 is actually a "RT-PCR test." That stands for reverse transcriptase polymease chain reaction, in which the viral genome is goes through a reverse transcriptase reaction before going into the PCR reaction. Why must that be done before PCR?

Answer 1

Polymerase chain reaction (PCR) is a technique used to amplify small segments of DNA.Using PCR it is possible to generate thousands to millions of copies of a particular section of DNA from a very small amount of DNA.

Taq polymerase does not work on RNA samples, so PCR cannot be used directly to amplify RNA molecules.This is the enzyme that is in charge of replicating DNA.

Taq polymerase was identified as an enzyme able to withstand the protein-denaturing conditions (high temperature) required during PCR. Therefore, it replaced the DNA polymerase from E. coli originally used in PCR.

Corona virus possess a single-stranded RNA genome so that it is a retrovirus and cannot be amplified by PCR directly.

Reverse transcription, mostly used by retroviruses, involves the formation of a complementary DNA strand (cDNA) using an RNA template. The enzyme used in the reverse transcription is reverse transcriptase.

Since PCR cannot amply RNA genome,it is a must to go for reverse transcription reaction before it is introduced on to the PCR