Medical genetics: xeroderma pigmentosum: practice question

A Anatomy 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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Anatomy · Medical genetics: xeroderma pigmentosum

Sample item

A child has severe sunburn after minimal exposure, freckling of the face and several skin cancers by age 5. Which DNA repair process is deficient?

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

The answer and the reasoning

C. Nucleotide excision repair of pyrimidine dimers

Xeroderma pigmentosum is an autosomal recessive disorder in which nucleotide excision repair cannot remove UV-induced thymine dimers. The result is marked photosensitivity and early skin cancers.

Option by option

  • A. Homologous recombination of double-strand breaks

    Homologous recombination repair is defective in BRCA-related disease.

  • B. Base excision repair of oxidised bases

    Base excision repair corrects oxidative damage and is not the UV repair pathway.

  • C. Nucleotide excision repair of pyrimidine dimers (correct)

    Correct. Nucleotide excision repair removes UV-induced pyrimidine dimers.

  • D. Mismatch repair of replication errors

    Mismatch repair is defective in Lynch syndrome.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is C, Nucleotide excision repair of pyrimidine dimers. Xeroderma pigmentosum is an autosomal recessive disorder in which nucleotide excision repair cannot remove UV-induced thymine dimers.

Why is "Homologous recombination of double-strand breaks" not the answer?

Homologous recombination repair is defective in BRCA-related disease.

Why is "Base excision repair of oxidised bases" not the answer?

Base excision repair corrects oxidative damage and is not the UV repair pathway.

Why is "Mismatch repair of replication errors" not the answer?

Mismatch repair is defective in Lynch syndrome.

What concept does this question test?

It tests Medical genetics: xeroderma pigmentosum in Anatomy. The result is marked photosensitivity and early skin cancers.

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 Medical genetics: xeroderma pigmentosum?

Learn every nerve by its route, its muscles and what a lesion looks like at the bedside. That one habit answers a large share of questions. Then use the flashcards and the other Anatomy 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.