Concept
Lac operon
Model of inducible gene regulation
LAK OP-er-on
High-yield clue
The lac operon is turned on by lactose (via allolactose freeing the repressor) and turned up by low glucose through CAP-cAMP.
Overview
A cluster of E. coli genes for lactose metabolism controlled together as a unit, and the classic teaching model of an inducible operon. It shows negative control by a repressor plus positive control by catabolite (glucose) signaling.
Classification
- Inducible operon
- Negative control by LacI repressor
- Positive control by CAP-cAMP
- Structural genes lacZ/lacY/lacA
Lab & identification clues
- Operator/promoter regulatory-region vocabulary
- Allolactose inducer concept
- Catabolite-repression (glucose effect) vocabulary
Associations
- E. coli lactose utilization
- Model of prokaryotic gene regulation
- Reporter-gene lacZ study use
Commonly confused with
- Trp operon (repressible)
- Quorum sensing
Your notes
Original microbiology concept summary. Sources checked: OpenStax Microbiology 2e, NCBI Bookshelf Medical Microbiology, and CDC/WHO topic pages where applicable; reviewed 2026-06. Educational only; no diagnosis, treatment selection, infection-control instructions, or specimen-handling guidance.