Genetics: Down syndrome translocation: 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: Down syndrome translocation

Sample item

A phenotypically normal mother carries a 14;21 Robertsonian translocation. What is the approximate risk of Down syndrome in her offspring?

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

The answer and the reasoning

B. 10 to 15 percent

A female carrier of a 14;21 translocation has about a 10 to 15 percent risk of an affected child, while a male carrier has about 2 to 5 percent. A 21;21 translocation carrier has a 100 percent risk. Karyotyping of parents is vital in translocation cases.

Option by option

  • A. 50 percent

    A 50 percent figure applies to autosomal dominant disease.

  • B. 10 to 15 percent (correct)

    Correct. Roughly 10 to 15 percent for a female carrier.

  • C. 100 percent

    A 100 percent risk applies to 21;21 translocation.

  • D. Less than 1 percent

    The risk is higher than the general population risk.

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 B, 10 to 15 percent. A female carrier of a 14;21 translocation has about a 10 to 15 percent risk of an affected child, while a male carrier has about 2 to 5 percent.

Why is "50 percent" not the answer?

A 50 percent figure applies to autosomal dominant disease.

Why is "100 percent" not the answer?

A 100 percent risk applies to 21;21 translocation.

Why is "Less than 1 percent" not the answer?

The risk is higher than the general population risk.

What concept does this question test?

It tests Genetics: Down syndrome translocation in Pediatrics. A 21;21 translocation carrier has a 100 percent risk. Karyotyping of parents is vital in translocation cases.

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 Genetics: Down syndrome translocation?

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.