What happens to transcription when an inducible operon is exposed to its inducer?

• A. Translation is initiated independently of transcription.
• B. Transcription is activated.
• C. The promoter is degraded.
• D. Permanently halted.

Answer: (B)

Inducible operons are kept off by a repressor bound to the operator. When the inducer is present, it binds the repressor and changes its shape, causing the repressor to release from the operator. With the operator free, RNA polymerase can bind to the promoter and begin transcription of the downstream genes. So transcription is activated in response to the inducer. The inducer doesn’t directly trigger translation, and it doesn’t degrade the promoter or cause transcription to be permanently halted; once the inducer is removed (and the repressor can rebind), the system can switch back to the off state.