Evolution and speciation · USMLE Step 1

Which of the following best defines biological evolution in a population genetics context?

  1. Change in an individual’s DNA during its lifetime
  2. Change in allele frequencies within a population over time
  3. Change in protein structure caused by a mutation
  4. Change in a species driven by individual migration events
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Correct answer: Change in allele frequencies within a population over time

Evolution in population genetics refers to changes in allele frequencies across generations within a population, not changes within an individual’s lifetime.

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