Genetics: Duchenne inheritance: 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: Duchenne inheritance

Sample item

A woman has a brother and a son with Duchenne muscular dystrophy. What is the risk for her next male child?

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

The answer and the reasoning

A. 50 percent affected

Duchenne muscular dystrophy is X-linked recessive, and a carrier mother transmits the mutated X to half of her sons, who are affected, and half of her daughters, who become carriers. Her serum CK may be mildly raised. New mutations explain about one third of cases.

Option by option

  • A. 50 percent affected (correct)

    Correct. A carrier mother has a 50 percent risk for each son.

  • B. 25 percent affected

    Twenty-five percent is the risk for each child in an autosomal recessive cross.

  • C. No risk

    She is an obligate carrier.

  • D. 100 percent affected

    Not all sons are affected.

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 A, 50 percent affected. Duchenne muscular dystrophy is X-linked recessive, and a carrier mother transmits the mutated X to half of her sons, who are affected, and half of her daughters, who become carriers.

Why is "25 percent affected" not the answer?

Twenty-five percent is the risk for each child in an autosomal recessive cross.

Why is "No risk" not the answer?

She is an obligate carrier.

Why is "100 percent affected" not the answer?

Not all sons are affected.

What concept does this question test?

It tests Genetics: Duchenne inheritance in Pediatrics. Her serum CK may be mildly raised. New mutations explain about one third of cases.

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: Duchenne inheritance?

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.