🧬
Operon Regulation (Lac vs Trp)
AP Biology · Unit 6 Gene Expression
Learning Objectives
Operon Structure: Promoter (binds RNAP), Operator (binds Repressor), Genes.
Inducible (Lac): Normally OFF. Turned ON by presence of Lactose (Inducer) which disables repressor.
Repressible (Trp): Normally ON. Turned OFF by presence of Tryptophan (Corepressor) which activates repressor.
Tags
Gene ExpressionOperonRepressorTranscription
Select Operon System
The Lac Operon codes for enzymes that break down lactose. It is normally OFF because an active repressor is bound to the operator, preventing RNA Polymerase from transcribing.
Environment Molecule
Add Lactose
TRANSCRIPTION OFF
Key AP Exam Tip
Inducible operons function in Catabolic (breaking down) pathways; you only want the enzymes when the food is present.