Lac operon system

lacl gene

codes for repressor protein that inhibits transcription when lactose is absent

lacP

promoter: site where RNA polymerase binds to initiate transcription of the structural genes

lacO

operator: region where the repressor protein binds to block RNA polymerase from transcribing the structural genes

lacZ

encodes beta-galactosidase

lacY

encodes permease

beta-galactosidase

enzyme that breaks down lactose into glucose and galactose

permease

facilitates the entry of lactose into the bacteria cell

lacA

encodes transacetylase

transacetylase

gene whose exact function is less understood but is thought to be involved in lactose metabolism

CAP-cAMP complex

stimulates transcription in the lac operon

trp operon

another operon system, this one produces tryptophan

negative repressible

which type of regulation is the trp operon