Medical genetics: X-linked dominant inheritance: 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: X-linked dominant inheritance

Sample item

In a family with hypophosphataemic rickets, an affected man has affected daughters but all of his sons are unaffected. Affected women pass the disorder to half of their children of either sex. Which mode of inheritance fits?

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

The answer and the reasoning

D. X-linked dominant

In X-linked dominant inheritance, an affected father transmits the gene to all his daughters and to none of his sons because sons receive his Y chromosome. Affected heterozygous women transmit it to half of their children.

Option by option

  • A. X-linked recessive

    X-linked recessive disease would usually spare daughters of an affected man, who would be carriers.

  • B. Mitochondrial

    Mitochondrial inheritance passes only through the mother to all children.

  • C. Autosomal dominant

    Autosomal dominant inheritance allows male-to-male transmission, so affected fathers would pass it to sons.

  • D. X-linked dominant (correct)

    Correct. No male-to-male transmission with all daughters of an affected man affected is the hallmark.

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 D, X-linked dominant. In X-linked dominant inheritance, an affected father transmits the gene to all his daughters and to none of his sons because sons receive his Y chromosome.

Why is "X-linked recessive" not the answer?

X-linked recessive disease would usually spare daughters of an affected man, who would be carriers.

Why is "Mitochondrial" not the answer?

Mitochondrial inheritance passes only through the mother to all children.

Why is "Autosomal dominant" not the answer?

Autosomal dominant inheritance allows male-to-male transmission, so affected fathers would pass it to sons.

What concept does this question test?

It tests Medical genetics: X-linked dominant inheritance in Anatomy. Affected heterozygous women transmit it to half of their children.

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: X-linked dominant inheritance?

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.