Question

Which of the following drugs acts by inhibiting the transcription of DNA to RNA ?

• A. Rifampicin
• B. Nitrofurantoin
• C. Ciprofloxacin
• D. Novobiocin

Answer 1

The Correct Option is A

Map each drug to the step of the central dogma it attacks. Transcription (DNA to RNA) needs RNA polymerase, so look for the RNA polymerase blocker.
Rifampicin clamps onto the beta subunit of bacterial DNA-dependent RNA polymerase and stops RNA synthesis at the initiation step. This single mechanism is why it is also a cornerstone antitubercular drug and a prophylactic against meningococcus.
The distractors hit other steps: ciprofloxacin and novobiocin interfere with DNA gyrase during replication, and nitrofurantoin generates reactive metabolites that broadly damage bacterial macromolecules. None of them act on transcription, so rifampicin is the answer.