1. Inducible operon
2. Three proteins: β-galactosidase, permease, transacetylase
3. The lac repressor protein binds to the operator region and blocks RNA polymerase from transcribing the structural genes.
4. Lactose (or allolactose) acts as an inducer by binding to the repressor, causing a conformational change that prevents it from binding to the operator.
5. When the repressor is not bound to the operator, RNA polymerase can bind to the promoter and transcribe the structural genes.
6. If lactose is present but glucose is also present, cAMP levels are low, so CAP cannot bind to the CAP site; transcription occurs at a low level because the repressor is removed but CAP activation is absent.
7. Transcription is turned ON when lactose is present (repressor inactivated) AND glucose is absent (CAP activated by cAMP).
Parent Tip: Review the logic above to help your child master the concept of lac operon worksheet.
