Genetics: Prader-Willi syndrome: practice question

A Pediatrics 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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Pediatrics · Genetics: Prader-Willi syndrome

Sample item

A floppy infant with poor feeding grows into a child with hyperphagia, obesity, hypogonadism and mild intellectual disability. What is the mechanism?

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

The answer and the reasoning

D. Loss of paternal 15q11-13 genes by deletion or maternal uniparental disomy

Prader-Willi syndrome results from absent paternally inherited 15q11-13 expression, by paternal deletion in about 70 percent or maternal uniparental disomy. Angelman syndrome results from loss of the maternal copy (UBE3A). Both are examples of genomic imprinting.

Option by option

  • A. FMR1 expansion

    FMR1 expansion causes fragile X.

  • B. Trisomy 15

    Trisomy 15 is not the mechanism.

  • C. Loss of maternal 15q11-13 alleles

    Loss of maternal genes causes Angelman syndrome.

  • D. Loss of paternal 15q11-13 genes by deletion or maternal uniparental disomy (correct)

    Correct. Absence of paternal genes gives Prader-Willi.

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 Pediatrics question

What is the answer to this Pediatrics question?

The best answer is D, Loss of paternal 15q11-13 genes by deletion or maternal uniparental disomy. Prader-Willi syndrome results from absent paternally inherited 15q11-13 expression, by paternal deletion in about 70 percent or maternal uniparental disomy.

Why is "FMR1 expansion" not the answer?

FMR1 expansion causes fragile X.

Why is "Trisomy 15" not the answer?

Trisomy 15 is not the mechanism.

Why is "Loss of maternal 15q11-13 alleles" not the answer?

Loss of maternal genes causes Angelman syndrome.

What concept does this question test?

It tests Genetics: Prader-Willi syndrome in Pediatrics. Angelman syndrome results from loss of the maternal copy (UBE3A). Both are examples of genomic imprinting.

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 Genetics: Prader-Willi syndrome?

Memorise milestones and the vaccine schedule as tables and revise them often. Then use the flashcards and the other Pediatrics 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.