Question

The Center for Disease Control is using an RT-PCR based test as the primary clinical diagnostic method of establishing COVID-19 infection. Why is the reverse transcription step necessary in this test?

Answer 1

The coronavirus (COVID-19) is a RNA virus which means it has RNA as the genetic material. In PCR, only DNA can be amplified using heat stable DNA polymerases such as Taq polymerase, so that it reaches a large enough quantity whichcan be detected. But since, coronavirus is a RNA virus, direct PCR cannot be used to amplify any specific part of its genetic material. So, RT-PCR is used where first, by reverse transcription, the RNA of coronavirus is converted to DNA and then the PCR process is carried out which amplifies the DNA of the coronavirus and finally the presence or absence of the virus is detected.