Molecular biology and genetics: rho-dependent transcription termination: 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 and genetics: rho-dependent transcription termination

Sample item

In E. coli, transcription of some genes ends without a stem-loop followed by a run of uridines. Which protein terminates transcription at these genes?

ARho factor, an ATP-dependent RNA helicaseBRelease factor RF1, which recognises stop codonsCSigma factor, which leaves the core enzymeDElongation factor Tu, which delivers aminoacyl-tRNA

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

The answer and the reasoning

A. Rho factor, an ATP-dependent RNA helicase

Bacterial transcription terminates by two mechanisms. Intrinsic termination uses a GC-rich hairpin followed by uridines, and rho-dependent termination uses the rho protein, which binds nascent RNA, uses ATP to move along it and dislodges RNA polymerase. Rho is inhibited by bicyclomycin.

Option by option

A. Rho factor, an ATP-dependent RNA helicase (correct)
Correct. Rho uses its helicase activity to release the transcript.
B. Release factor RF1, which recognises stop codons
RF1 acts in translation termination at stop codons.
C. Sigma factor, which leaves the core enzyme
Sigma factor directs initiation and dissociates after initiation, not at termination.
D. Elongation factor Tu, which delivers aminoacyl-tRNA
EF-Tu is a translation elongation factor.

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.

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, Rho factor, an ATP-dependent RNA helicase. Bacterial transcription terminates by two mechanisms.

Why is "Release factor RF1, which recognises stop codons" not the answer?

RF1 acts in translation termination at stop codons.

Why is "Sigma factor, which leaves the core enzyme" not the answer?

Sigma factor directs initiation and dissociates after initiation, not at termination.

Why is "Elongation factor Tu, which delivers aminoacyl-tRNA" not the answer?

EF-Tu is a translation elongation factor.

What concept does this question test?

It tests Molecular biology and genetics: rho-dependent transcription termination in Biochemistry. Intrinsic termination uses a GC-rich hairpin followed by uridines, and rho-dependent termination uses the rho protein, which binds nascent RNA, uses ATP to move along it and dislodges RNA polymerase. Rho is inhibited by bicyclomycin.

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 and genetics: rho-dependent transcription termination?

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.