BioCoach ActivityBack to BioCoach Main
BioCoach Contents
The lac Operon in E. coli
Concept 2: The Lactose Operon
   Review (2 pages)
Concept 5: The Lac Repressor Protein
   Review (1 page)
Concept 5: The Lac Repressor Protein
In the absence of lactose, the Lac repressor binds to the operator and keeps RNA polymerase from transcribing the lac genes.
Animate
It would be energetically wasteful for E. coli if the lac genes were expressed when lactose was not present.

The effect of the Lac repressor on the lac genes is referred to as negative regulation.