This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
[{'content': 'In E.coli structural gene of lac operon is stimulated in \nSelect and explain. \nA. Presence of glucose only, B. Presence of lactose only, C. Presence of glucose and absence of lactose, D. Presence of lactose and absence of glucose', 'role': 'user'}, {'content': 'Answer: D \nExplanation: JACOB and MONAD theory was based on the observation on lactose metabolism in E.coli Cell grown in glucose medium does not contain beta-galactosidase But when cells are transferred to medium containing only lactose, then the enzyme level in the cell increases several thousand foldsRef: DM Vasudevan, 7th edition, page no: 617', 'role': 'assistant'}]