Tetracycline stops protein synthesis in bacteria. Which statement correctly describes its mechanism?

Tetracycline stops protein synthesis in bacteria. Which statement correctly describes its mechanism?

• A. It binds to the codon on mRNA and prevents tRNA anticodon from pairing.
• B. It binds to DNA and stops transcription.
• C. It increases ribosome speed.
• D. It prevents protein synthesis by degrading mRNA.

Answer: (A)

Tetracycline works by blocking translation at the ribosome. It binds reversibly to the bacterial 30S ribosomal subunit and prevents aminoacyl-tRNA from entering the A site, so the tRNA anticodon cannot pair with the mRNA codon. With no tRNA able to bind at the A site, elongation cannot proceed and protein synthesis stops, which is why tetracycline is bacteriostatic. The idea that it binds to a codon on mRNA is not how this drug works, and the other options describe mechanisms that tetracycline does not use—interfering with transcription by binding DNA, speeding up ribosomes, or degrading mRNA.

Tetracycline works by blocking translation at the ribosome. It binds reversibly to the bacterial 30S ribosomal subunit and prevents aminoacyl-tRNA from entering the A site, so the tRNA anticodon cannot pair with the mRNA codon. With no tRNA able to bind at the A site, elongation cannot proceed and protein synthesis stops, which is why tetracycline is bacteriostatic.

The idea that it binds to a codon on mRNA is not how this drug works, and the other options describe mechanisms that tetracycline does not use—interfering with transcription by binding DNA, speeding up ribosomes, or degrading mRNA.