Haematology: haemophilia A inheritance: practice question

A Pathology 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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Pathology · Haematology: haemophilia A inheritance

Sample item

A man with severe haemophilia A and a woman with no family history of bleeding plan to have children. What outcome is expected?

AAll children will be normal and none will carry the geneBAll daughters will be carriers and no sons will be affectedCHalf the sons will be affected and half the daughters carriersDAll sons will be affected and all daughters normal

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

The answer and the reasoning

B. All daughters will be carriers and no sons will be affected

Haemophilia A is an X-linked recessive disorder from factor VIII deficiency. An affected father passes his single X chromosome to all daughters, who become obligate carriers, and passes his Y chromosome to sons, who are therefore unaffected. Carrier mothers pass the disease to half their sons.

Option by option

A. All children will be normal and none will carry the gene
Daughters of an affected father always inherit his X chromosome and are carriers.
B. All daughters will be carriers and no sons will be affected (correct)
Correct. Father-to-son transmission cannot occur in X-linked inheritance.
C. Half the sons will be affected and half the daughters carriers
This ratio applies to a carrier mother and a normal father, not to an affected father.
D. All sons will be affected and all daughters normal
Sons receive the Y chromosome from the father and cannot inherit the X-linked allele from him.

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.

Questions about this Pathology question

What is the answer to this Pathology question?

The best answer is B, All daughters will be carriers and no sons will be affected. Haemophilia A is an X-linked recessive disorder from factor VIII deficiency.

Why is "All children will be normal and none will carry the gene" not the answer?

Daughters of an affected father always inherit his X chromosome and are carriers.

Why is "Half the sons will be affected and half the daughters carriers" not the answer?

This ratio applies to a carrier mother and a normal father, not to an affected father.

Why is "All sons will be affected and all daughters normal" not the answer?

Sons receive the Y chromosome from the father and cannot inherit the X-linked allele from him.

What concept does this question test?

It tests Haematology: haemophilia A inheritance in Pathology. An affected father passes his single X chromosome to all daughters, who become obligate carriers, and passes his Y chromosome to sons, who are therefore unaffected. Carrier mothers pass the disease to half their sons.

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 Haematology: haemophilia A inheritance?

Learn each disease as a bundle: cause, key histology, markers, and the clinical hallmark. Then use the flashcards and the other Pathology 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.