Medical genetics: pedigree: 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: pedigree

Sample item

A disorder is seen in three generations of a family. An affected man has both an affected son and an affected daughter, and the disorder appears in every generation. Which mode of inheritance is most likely?

AMitochondrialBX-linked dominantCAutosomal dominantDAutosomal recessive

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

The answer and the reasoning

C. Autosomal dominant

Autosomal dominant inheritance shows vertical transmission, with affected individuals in each generation, equal involvement of both sexes, and male-to-male transmission. Each child of an affected heterozygote has a 50% chance of inheriting the allele. Male-to-male transmission rules out X-linkage.

Option by option

A. Mitochondrial
Mitochondrial disease is transmitted only by affected mothers, not fathers.
B. X-linked dominant
In X-linked dominant disease an affected father cannot pass the gene to his sons.
C. Autosomal dominant (correct)
Correct. Vertical transmission with male-to-male transmission fits autosomal dominant inheritance.
D. Autosomal recessive
Autosomal recessive disease typically skips generations and both parents are usually unaffected carriers.

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 Anatomy question

What is the answer to this Anatomy question?

The best answer is C, Autosomal dominant. Autosomal dominant inheritance shows vertical transmission, with affected individuals in each generation, equal involvement of both sexes, and male-to-male transmission.

Why is "Mitochondrial" not the answer?

Mitochondrial disease is transmitted only by affected mothers, not fathers.

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

In X-linked dominant disease an affected father cannot pass the gene to his sons.

Why is "Autosomal recessive" not the answer?

Autosomal recessive disease typically skips generations and both parents are usually unaffected carriers.

What concept does this question test?

It tests Medical genetics: pedigree in Anatomy. Each child of an affected heterozygote has a 50% chance of inheriting the allele. Male-to-male transmission rules out X-linkage.

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: pedigree?

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.