Nucleotide metabolism: 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.

Try it

Biochemistry · Nucleotide metabolism

Sample item

A 4-year-old boy has intellectual disability, dystonia, self-mutilation and hyperuricaemia. Which enzyme is deficient?

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

The answer and the reasoning

A. HGPRT

Lesch–Nyhan syndrome is an X-linked recessive deficiency of HGPRT in the purine salvage pathway. Purines are degraded to uric acid instead of being recycled, so uric acid rises and neurological features appear.

Option by option

  • A. HGPRT (correct)

    Correct. Self-biting plus gout-like picture points to Lesch–Nyhan.

  • B. Glucose-6-phosphatase

    Glucose-6-phosphatase deficiency causes von Gierke disease.

  • C. Adenosine deaminase

    ADA deficiency is an autosomal recessive cause of SCID.

  • D. Xanthine oxidase

    Xanthine oxidase deficiency lowers uric acid.

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.

More Biochemistry questions

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, HGPRT. Lesch–Nyhan syndrome is an X-linked recessive deficiency of HGPRT in the purine salvage pathway.

Why is "Glucose-6-phosphatase" not the answer?

Glucose-6-phosphatase deficiency causes von Gierke disease.

Why is "Adenosine deaminase" not the answer?

ADA deficiency is an autosomal recessive cause of SCID.

Why is "Xanthine oxidase" not the answer?

Xanthine oxidase deficiency lowers uric acid.

What concept does this question test?

It tests Nucleotide metabolism in Biochemistry. Purines are degraded to uric acid instead of being recycled, so uric acid rises and neurological features appear.

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 Nucleotide metabolism?

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.