What additional step is required for RT-PCR and why?

• A. Denaturation converts RNA into cDNA.
• B. Reverse transcription converts RNA into complementary DNA (cDNA) so it can be amplified by DNA polymerase.
• C. Ligation attaches adapters to DNA to enable amplification.
• D. The reaction is performed without any polymerase.

Answer: (B)

RT-PCR must start from RNA, but standard PCR amplifies DNA. To bridge that gap, an extra step is needed to turn the RNA into a DNA template that the DNA polymerase can copy. This step uses reverse transcriptase to synthesize complementary DNA (cDNA) from the RNA. Once the cDNA is made, PCR can amplify it just like any other DNA template, producing many copies that reflect the original RNA sequence. The other options don’t fit because denaturation is about separating double-stranded DNA during cycling, not converting RNA to DNA; ligation with adapters is a preparation step for other workflows like sequencing; and running the reaction without a polymerase would not amplify anything.