Genetic and Pediatric Diseases · USMLE Step 1

Which of the following syndromes is an example of a non-Mendelian, imprinting or uniparental disomy disorder rather than classic autosomal or chromosomal abnormality?

  1. Cystic fibrosis
  2. Prader–Willi syndrome
  3. Turner syndrome
  4. Sickle cell disease
Show answer and explanation

Correct answer: Prader–Willi syndrome

Prader–Willi syndrome typically arises from lack of paternal allele expression on chromosome 15 — either by paternal deletion or maternal uniparental disomy — an imprinting disorder distinct from classic Mendelian inheritance.

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