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': 'A prokaryotic regulatory gene synthesizes a protein known as: \nSelect and explain. \nA. The promoter, B. The operator, C. The repressor, D. The enhancer', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The repressor is the protein produced by the regulatory gene. The promoter is not a protein, but a region of the gene (or operon) where RNA polymerase binds to initiate transcription. The operator is not a protein, but a region of the promoter where the repressor binds, thus blocking the movement of RNA polymerase into the gene. The enhancer is found in eukaryotes only and is a region of DNA which binds regulatory proteins which then interact with promoter regions to affect the rate of transcription. The inducer is generally not a protein, but a metabolite that combines with the repressor to inactivate it, thus allowing RNA polymerase to bind to the promoter.', 'role': 'assistant'}]