<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 33-year-old man presents to his physician with a 3-year history of gradually worsening tics and difficulty walking. He was last seen by the physician 5 years ago for anxiety, and he has been buying anti-anxiety medications from an internet website without a prescription as he cannot afford to pay for doctors visits. Now, the patient notes that his anxiety is somewhat controlled, but motor difficulties are making it difficult for him to work and socialize. Family history is unobtainable as his parents died in an accident when he was an infant. He grew up in foster care and was always a bright child. An MRI of the brain is ordered; it shows prominent atrophy of the caudate nucleus. Repeats of which of the following trinucleotides are most likely responsible for this patients disorder?? A: CCG, B: CGG, C: GAA, D: CAG, E: CTG,  <response>: This is a clinical vignette describing a 33-year-old man with a 3-year history of worsening tics and difficulty walking. He has a history of anxiety. The MRI shows atrophy of the caudate nucleus. Based on the clinical presentation of tics, movement issues, and caudate atrophy, this patient likely has Huntingtons disease. Huntingtons disease is caused by a trinucleotide repeat expansion in the HTT gene. The specific trinucleotide repeat is CAG, which codes for glutamine. Expansion of the CAG repeats in HTT leads to production of mutant huntingtin protein and subsequent neurodegeneration.Therefore, the answer is D, as CAG repeats are most likely responsible for this patients disorder.D: CAG 