A 45-year-old man with no significant past medical history undergoes elective knee arthroscopy under general anesthesia. After receiving succinylcholine 1.5 mg/kg IV for rapid sequence intubation, he develops severe, sustained muscle rigidity within seconds. His core temperature rises to 39.5°C, heart rate increases to 136 bpm, and end-tidal CO2 rises sharply to 65 mmHg. Laboratory studies obtained 2 hours post-operatively reveal serum potassium 7.4 mEq/L, creatine kinase 12,000 U/L, and dark brown urine. The anesthesiologist notes that rocuronium (a non-depolarizing agent) administered after succinylcholine produced normal paralysis. His brother required emergency treatment for an identical reaction during surgery 20 years ago. Which of the following genetic abnormalities best explains this clinical presentation?

1. A)Mutation in the ryanodine receptor (RYR1) geneGABARITO
2. B)Loss-of-function mutation in the butyrylcholinesterase (BCHE) gene
3. C)Autosomal recessive mutation affecting acetylcholinesterase
4. D)Gain-of-function mutation in the nicotinic acetylcholine receptor alpha subunit
5. E)X-linked mutation in the dystrophin gene