Mendelian inheritance · USMLE Step 1

A disease shows increasing severity and earlier onset in successive generations. Which genetic concept explains this pattern?

  1. Genetic anticipation
  2. Variable expressivity
  3. Incomplete penetrance
  4. X-linked dominance
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Correct answer: Genetic anticipation

Genetic anticipation refers to worsening disease severity or earlier onset across generations, often related to trinucleotide repeat expansion. Expressivity deals with severity variability without generational change.

Difficulty: Medium Question 20 of 20

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