Genetics: mitochondrial 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: mitochondrial inheritance

Sample item

A family shows a disease transmitted from affected mothers to all of their children but never from affected fathers. Which pattern is this?

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

The answer and the reasoning

B. Mitochondrial inheritance

Mitochondrial DNA is transmitted by the ovum, so all offspring of an affected mother can inherit it, while affected fathers do not pass it on. Heteroplasmy causes variable expression. Examples are MELAS, MERRF and Leber hereditary optic neuropathy.

Option by option

  • A. Y-linked

    Y-linked disease passes from father to sons only.

  • B. Mitochondrial inheritance (correct)

    Correct. Maternal transmission to all children suggests mitochondrial inheritance.

  • C. Autosomal dominant

    Autosomal dominant disease passes from either parent.

  • D. X-linked dominant

    X-linked dominant disease can pass from fathers to all daughters.

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, Mitochondrial inheritance. Mitochondrial DNA is transmitted by the ovum, so all offspring of an affected mother can inherit it, while affected fathers do not pass it on.

Why is "Y-linked" not the answer?

Y-linked disease passes from father to sons only.

Why is "Autosomal dominant" not the answer?

Autosomal dominant disease passes from either parent.

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

X-linked dominant disease can pass from fathers to all daughters.

What concept does this question test?

It tests Genetics: mitochondrial inheritance in Pediatrics. Heteroplasmy causes variable expression. Examples are MELAS, MERRF and Leber hereditary optic neuropathy.

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: mitochondrial 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.