This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'Mutation in sickle cell disease is a \nSelect and explain. \nA. Silence mutation, B. Missense mutation, C. Nonsense mutation, D. Frame shift mutation', 'role': 'user'}, {'content': 'Answer: B \nExplanation: It is a point mutation at the 6th code of\xa0β globin chain leading to substitution of glutamine by valine.', 'role': 'assistant'}]