Mitochondrial inheritance · USMLE Step 1

Which term describes a condition in which some cells in a person’s body have mutated mtDNA and others have normal mtDNA, leading to variable expression of a mitochondrial disease?

  1. Homoplasmy
  2. Heterozygosity
  3. Heteroplasmy
  4. Mosaicism in nuclear DNA
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Correct answer: Heteroplasmy

Heteroplasmy refers to the presence of both mutant and wild-type mtDNA within the same individual’s cells, leading to variability in which tissues are affected and disease severity.

Difficulty: Medium Question 11 of 19

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