Mendelian inheritance · USMLE Step 1

A lethal autosomal dominant mutation reduces survival before reproduction. What is expected in the population?

  1. Allele frequency increases
  2. Allele frequency remains constant
  3. Allele frequency decreases
  4. No effect on allele frequency
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Correct answer: Allele frequency decreases

A lethal dominant mutation prevents affected individuals from reproducing, reducing allele frequency. Such mutations must arise de novo to persist. This is an example of strong negative selection.

Difficulty: Medium Question 13 of 20

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