Molecular biology: RNA interference: 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: RNA interference

Sample item

Patisiran, a double-stranded small interfering RNA given intravenously for hereditary transthyretin amyloidosis, lowers circulating transthyretin. Which mechanism applies?

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

The answer and the reasoning

A. The guide strand loads into RISC and pairs with transthyretin mRNA, which Argonaute cleaves

Small interfering RNAs are loaded into the RNA-induced silencing complex. The guide strand pairs with near-perfect complementarity to its target mRNA and Argonaute cleaves the transcript, lowering protein synthesis. MicroRNAs use the same complex but pair imperfectly, causing translational repression and mRNA decay.

Option by option

  • A. The guide strand loads into RISC and pairs with transthyretin mRNA, which Argonaute cleaves (correct)

    Correct. RISC-guided cleavage of the target mRNA is the mechanism of an siRNA.

  • B. The drug binds the promoter of the transthyretin gene and blocks RNA polymerase II

    RNA interference acts after transcription on mRNA and does not block the promoter.

  • C. The drug is reverse transcribed into DNA that silences the gene

    siRNA is not reverse transcribed, and human cells do not integrate it into DNA.

  • D. The drug blocks ribosome binding by attaching to the 5' cap of mRNA

    The siRNA does not target the 5' cap, and it works by complementary pairing with mRNA.

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, The guide strand loads into RISC and pairs with transthyretin mRNA, which Argonaute cleaves. Small interfering RNAs are loaded into the RNA-induced silencing complex.

Why is "The drug binds the promoter of the transthyretin gene and blocks RNA…" not the answer?

RNA interference acts after transcription on mRNA and does not block the promoter.

Why is "The drug is reverse transcribed into DNA that silences the gene" not the answer?

siRNA is not reverse transcribed, and human cells do not integrate it into DNA.

Why is "The drug blocks ribosome binding by attaching to the 5' cap of mRNA" not the answer?

The siRNA does not target the 5' cap, and it works by complementary pairing with mRNA.

What concept does this question test?

It tests Molecular biology: RNA interference in Biochemistry. The guide strand pairs with near-perfect complementarity to its target mRNA and Argonaute cleaves the transcript, lowering protein synthesis. MicroRNAs use the same complex but pair imperfectly, causing translational repression and mRNA decay.

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: RNA interference?

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.