Mitochondrial inheritance · USMLE Step 1

In a family pedigree for a mitochondrial disease, which of the following patterns is expected if the disease is due to an mtDNA mutation?

  1. Affected fathers transmit the disease to all of their children
  2. Only the male children in the family are ever affected
  3. Both sexes affected, but only through affected mothers
  4. The trait appears only in siblings of the parent's sex
Show answer and explanation

Correct answer: Both sexes affected, but only through affected mothers

Because mtDNA is maternally inherited, both sons and daughters of an affected mother can be affected; affected fathers do not transmit it because paternal mitochondria are excluded.

Difficulty: Medium Question 2 of 19

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