A newborn has a cleft lip, polydactyly and holoprosencephaly. Which trisomy is most likely?
Answer and explanation
Correct answer: A. Trisomy 13
- Step 1: Patau syndrome has these midline defects. Answer: Trisomy 13. Why not the others: Edwards syndrome has rocker-bottom feet and clenched fists, Down syndrome is milder and Turner is monosomy X.
Practise more Biochemistry and Genetics.
Free questions with an explanation for every one, and full timed USMLE Step 1 mock tests.
More Biochemistry and Genetics questions
- A child has megaloblastic anemia and orotic aciduria without hyperammonemia. Which supplement treats this?
- A 20-year-old has recurrent pancreatitis, pulmonary infections and infertility. Which gene is defective?
- A 50-year-old alcoholic has confusion, ataxia and ophthalmoplegia. Which vitamin is deficient?
- A 25-year-old has recurrent sinus infections and infertility. Chest imaging shows dextrocardia. Which structure is defective?
- A child has hypotonia, a flat facial profile and a single palmar crease. What is the most common cause of this syndrome?
- A sailor has bleeding gums, perifollicular hemorrhages and poor wound healing. Which process is impaired?