Mendelian inheritance · USMLE Step 1

A healthy couple has a child with an autosomal recessive metabolic disorder. Neither parent is affected. What is the probability that their next child will also be affected?

  1. 0%
  2. 25%
  3. 50%
  4. 75%
Show answer and explanation

Correct answer: 25%

Autosomal recessive disorders require inheritance of two mutant alleles. Two carriers have a 25% chance of producing an affected child. The remaining offspring are either carriers or unaffected.

Difficulty: Medium Question 1 of 20

Practice all 20 Mendelian inheritance questions

Keep practicing

More Mendelian inheritance questions