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: Biochemistry
[{'content': 'One of the following mutation is potentially lethal - \nSelect and explain. \nA. Substitution of adenine for cytosine, B. Substitution of methylcytosine for cytosine, C. Substitution of guanine for cytocine, D. Inseion of one base', 'role': 'user'}, {'content': 'Answer: D \nExplanation: D i.e. Inseion of one base', 'role': 'assistant'}]