Molecular biology: transcription: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Molecular biology: transcription

Sample item

A patient on antituberculous therapy is given a drug that inhibits bacterial DNA-dependent RNA polymerase. Which statement describes the mechanism?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. Rifampicin binds the beta subunit and blocks initiation of transcription

Rifampicin binds the beta subunit of prokaryotic RNA polymerase and blocks RNA chain initiation. It does not inhibit the human enzyme. Alpha-amanitin, in contrast, inhibits eukaryotic RNA polymerase II.

Option by option

  • A. Rifampicin binds the beta subunit and blocks initiation of transcription (correct)

    Correct. Transcription initiation is blocked in bacteria.

  • B. Rifampicin inhibits peptidyl transferase

    Peptidyl transferase is inhibited by chloramphenicol.

  • C. Rifampicin binds the 30S ribosomal subunit

    The 30S subunit is bound by aminoglycosides and tetracyclines.

  • D. Rifampicin blocks DNA gyrase

    DNA gyrase is the target of fluoroquinolones.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, Rifampicin binds the beta subunit and blocks initiation of transcription. Rifampicin binds the beta subunit of prokaryotic RNA polymerase and blocks RNA chain initiation.

Why is "Rifampicin inhibits peptidyl transferase" not the answer?

Peptidyl transferase is inhibited by chloramphenicol.

Why is "Rifampicin binds the 30S ribosomal subunit" not the answer?

The 30S subunit is bound by aminoglycosides and tetracyclines.

Why is "Rifampicin blocks DNA gyrase" not the answer?

DNA gyrase is the target of fluoroquinolones.

What concept does this question test?

It tests Molecular biology: transcription in Biochemistry. It does not inhibit the human enzyme. Alpha-amanitin, in contrast, inhibits eukaryotic RNA polymerase II.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Molecular biology: transcription?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.