<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 32-year-old man presents to his primary care provider reporting weakness. He recently noticed that he has difficulty letting go of a doorknob or releasing his hand after shaking hands with others. His past medical history is notable for diabetes, for which he takes metformin. He drinks 2-3 beers per day, uses marijuana occasionally, and works as a security guard. His family history is notable for an early cardiac death in his father. His temperature is 98.6F 37C, blood pressure is 13085 mmHg, pulse is 85min, and respirations are 18min. On exam, there is notable muscle atrophy in his hands, feet, and neck. He has delayed hand grip release bilaterally and is slow to return from a smile to a neutral facial expression. His gait is normal, and Rombergs test is negative. He also has frontal balding. This patients condition is caused by a mutation in which of the following genes?? A: DMPK, B: DPC, C: Dystrophin, D: Frataxin, E: SMN1,  <response>: This is a clinical vignette describing a 32-year-old man with progressive weakness and difficulty releasing his grip, as well as facial muscle weakness and atrophy in his hands, feet and neck. The key findings are delayed relaxation of hand grip bilaterally, slow return to a neutral facial expression after smiling, and muscle atrophy in a distal distribution. This suggests an upper motor neuron disorder like ALS or a myotonic disorder. The frontal balding and diabetes also point towards myotonic dystrophy type 1, which is caused by an expanded trinucleotide repeat in the DMPK gene.A: DMPK 