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': 'Purpose of Gene therapy - \nSelect and explain. \nA. Replacement of abnormal gene by normal gene, B. Replacement of normal gene by abnormal gene, C. Knock out of abnormal gene, D. Introduction of viral gene', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The most common approach is to insert a normal gene into non-specific location within the genome to replace a non\xadfunctional gene (abnormal gene).', 'role': 'assistant'}]