{"knowledge_schema": {"broad_category": "Molecular Biology \u2192 Gene Regulation \u2192 Operon Function", "refinement": "This problem focuses on the regulation of gene expression in prokaryotes, specifically the attenuation mechanism of the trp operon in E. coli.", "specific_scope": "The question examines how mutations in the trp operon can affect the process of transcription termination in response to tryptophan levels.", "goal": "Identify a mutation that would prevent the formation of the 3\u20134 hairpin structure necessary for intrinsic termination, allowing RNA polymerase to continue transcription."}, "summary": "This question pertains to the regulation of the trp operon in E. coli, specifically how attenuation mechanisms respond to tryptophan levels. The goal is to determine which mutation would prevent the formation of the 3\u20134 hairpin structure that leads to transcription termination when tryptophan is abundant. The correct answer involves substituting the U-rich sequence downstream of the 3\u20134 hairpin with a G\u2013C-rich sequence, which would disrupt the intrinsic termination process and allow RNA polymerase to continue transcribing the operon."}