Which phenomenon explains why siblings of the same mother may have different severity of a mitochondrial disorder despite inheriting the same mutation?
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Correct answer: The mtDNA bottleneck combined with heteroplasmy
During oogenesis, only a small subset of mtDNA molecules is transmitted to the egg (the bottleneck), and random sampling can result in variable proportions of mutant vs. wild-type mtDNA in different children — leading to variable expression.
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More Mitochondrial inheritance questions
- Which structural feature of human mtDNA distinguishes it from nuclear DNA?
- Why do mitochondrial diseases often affect tissues with high energy demand (like brain and muscle)?
- Which of the following statements about recombination in human mitochondrial DNA is most accurate?
- Which of the following is a possible mechanism by which paternal mitochondria are excluded from inheritance in humans?
- If a woman carries a homoplasmic harmful mtDNA mutation, what is the risk that her child (regardless of sex) will inherit the mutation?
- Which of the following scenarios would argue against a strictly maternal mtDNA inheritance model in humans?