Mitochondrial inheritance · USMLE Step 1

Which of the following would be strong evidence for a nuclear (rather than mitochondrial) cause of a suspected mitochondrial disease?

  1. Trait transmitted only through affected mothers to offspring
  2. Affected fathers passing the disease to their children
  3. Both sexes affected but no clear maternal lineage pattern
  4. Disease severity correlating with mutant mtDNA load in tissues
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Correct answer: Affected fathers passing the disease to their children

If affected fathers transmit the disease to their children, this violates maternal-only mtDNA inheritance — suggesting that a nuclear gene (autosomal or X-linked) is responsible instead of mtDNA.

Difficulty: Medium Question 18 of 19

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