Why might a heteroplasmic mother have both affected and unaffected children when carrying a deleterious mtDNA mutation?
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Correct answer: Random bottleneck sampling giving eggs variable mutant load
Random partitioning of mtDNA during egg formation (bottleneck) can result in eggs with varying proportions of mutant vs wild-type mtDNA. Some eggs may carry low mutant load — yielding unaffected children — while others have high load — leading to disease in offspring.
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