Molecular Biology/Genetics USMLE Step 1 Practice Question
A 20-year-old male presents with progressive weakness and myotonia, most pronounced in the hands and feet. Vital signs show HR 78/min, BP 118/76 mmHg, RR 14/min. Serum creatine kinase is elevated at 2,200 U/L. Muscle biopsy demonstrates prominent ring fibers, centrally located nuclei, and disorganized sarcoplasmic masses. Cardiac examination reveals no arrhythmias. This condition has been associated with a mutation on which of the following chromosomes?
Answer choices
- A4
- B19Correct answer
- CY
- D5
- EX
- F9
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