Population genetics · USMLE Step 1

A population in which one allele becomes 100% prevalent has undergone:

  1. Fixation
  2. Mutation
  3. Gene flow
  4. Balanced polymorphism
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Correct answer: Fixation

Fixation occurs when an allele reaches 100% frequency. It commonly results from drift or strong selection. Balanced polymorphism maintains multiple alleles instead.

Difficulty: Medium Question 15 of 20

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