This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics, Subject name: Pathology
[{'content': "An example for gain of function mutation is? \nSelect and explain. \nA. Osteogenesis imperfecta, B. Ehler danlos syndrome, C. Marfan syndrome, D. Huntington's disease", 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. (d) Huntington's diseaseIn Huntington disease, the trinucleotide repeat mutation affecting the Huntington gene gives rise to an abnormal protein, called huntingtin, that is toxic to neurons causing neurologic deficit", 'role': 'assistant'}]