Gene Expression in Prokayotes Flashcards
Inducible systems
small molecules function to (induce) turn ON transcription
removes the repressor from the operator
Inducer
a small molecule that triggers removal of repressor from operator
Example of an inducible system
lac operon’s negative control
Repressible system
small molecule functions to (repress) turn OFF transcription
adds repressor to the operator
Corepressor
a small molecule that triggers the addition of repressor to operator
repressor is added to the operator through a shape change
Negative controls
in these systems, repressors serve to block transcription
inducers and repressible systems are both negative controls
Lac operon negative control
inducible repressor
when repressor is bound to allolactose, it is removed from the operator
allolactose is high when lactose is high (makes sense. removes repressor when lactose is high)
Lac operon positive control
Catabolite ACTIVATOR protein (CAP) can bind to DNA to activate transcription when cAMP is bound
cAMP is high when glucose is low (makes sense. allows lac operon to be expressed when not much glucose)
Active repressor and active activator what occurs
transcription is almost fully blocked
Inactive repressor and inactive activator what occurs
there is some transcription
What is a major difference in gene regulation of prokaryotes vs eukaryotes?
Prokaryotes default state is ON
Eukaryotes default state is OFF
example of a repressible system
trp operon in E. coli
produces tryptophan from other compounds when tryptophan is not present in the cell’s environment
Postive control
corresponds to activators
in these models, activators will turn on transcription
What part of the operon do activators bind to?
promoters
What part of the operon do repressors bind to?
operators
