Molecular biology and genetics: VHL and HIF: 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: VHL and HIF

Sample item

A 30-year-old has retinal and cerebellar haemangioblastomas and a clear cell renal carcinoma. A germline VHL mutation is found. What is the molecular consequence?

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

The answer and the reasoning

D. Failure to degrade HIF, increasing VEGF and erythropoietin expression

The VHL protein targets hypoxia-inducible factor for ubiquitin-mediated degradation under normal oxygen. Without it, HIF accumulates and switches on VEGF, PDGF and erythropoietin, giving vascular tumours and sometimes polycythaemia. The other options describe other tumour pathways.

Option by option

  • A. Failure to repair mismatched bases

    Mismatch repair failure causes Lynch syndrome.

  • B. Constitutive activation of RAS

    RAS activation is a different oncogenic mechanism.

  • C. Failure to phosphorylate Rb

    Rb phosphorylation is controlled by cyclin D with CDK4 and CDK6.

  • D. Failure to degrade HIF, increasing VEGF and erythropoietin expression (correct)

    Correct. Unchecked HIF drives angiogenic and erythropoietic gene expression.

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 D, Failure to degrade HIF, increasing VEGF and erythropoietin expression. The VHL protein targets hypoxia-inducible factor for ubiquitin-mediated degradation under normal oxygen.

Why is "Failure to repair mismatched bases" not the answer?

Mismatch repair failure causes Lynch syndrome.

Why is "Constitutive activation of RAS" not the answer?

RAS activation is a different oncogenic mechanism.

Why is "Failure to phosphorylate Rb" not the answer?

Rb phosphorylation is controlled by cyclin D with CDK4 and CDK6.

What concept does this question test?

It tests Molecular biology and genetics: VHL and HIF in Biochemistry. Without it, HIF accumulates and switches on VEGF, PDGF and erythropoietin, giving vascular tumours and sometimes polycythaemia. The other options describe other tumour pathways.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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: VHL and HIF?

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.