Mendelian inheritance · USMLE Step 1

A child expresses a phenotype that neither parent shows, but both parents are carriers. Which inheritance pattern best explains this?

  1. Autosomal dominant inheritance
  2. Autosomal recessive inheritance
  3. X-linked dominant inheritance
  4. Mitochondrial inheritance
Show answer and explanation

Correct answer: Autosomal recessive inheritance

Autosomal recessive traits require two copies of the mutant allele, so unaffected carriers may pass the disorder to offspring. This results in a classic 'skipping generations' pattern. Dominant traits would appear in at least one parent.

Difficulty: Medium Question 4 of 20

Practice all 20 Mendelian inheritance questions

Keep practicing

More Mendelian inheritance questions