what is an operon?
a cluster of functionally related genes (DNA) that is controlled by a single on-off switch
Is the promoter transcribed?
WHat is the operator?
segment of DNA that acts as the regulatory "switch"
What does an operon contain?
Transcription of the __ gene is always turned __; it is NOT __.
All of the structural genes of an operon are transcribed onto a single __ mRNA.
When the active repressor binds to the operator and blocks RNA polymerase, what happens to transcription?
it is blocked
This is a form of __ regulation.
What happens if tryptophan is absent?
repressor inactive and operon on
What happens if tryptophan is present?
repressor active and operon off
What is the default for the trp operon?
for transcription to occur
What enzyme gets lactose into the cell?
What is the default for the lac operon?
for transcription to be blocked and not occur
What happens if lactose absent?
repressor active, operon off
What happens if lactose is present?
repressor inactive, operon on
an activator of transcription?
catabolite activator protein
If cAMP binds to CAP, what happens?
CAP is actviated
What does activated CAP do?
attaches to promoter of lac operon and increases affinity for RNA pol
What kind of control is lactose under?
negative and positive from CAP
In the lac operon, what is transcription stimulated by?
presence of lactose and absence of glucose
In tryptophan, what is transcription stimulated by?
basece of tryptohan