Prokaryotic Gene Regulation Flashcards
what are prokaryotic genes controlled by?
operons
what is an operon?
is a stretch of DNA that includes the operator, promoter and the gene they control.
define RNA polymerase
is a transcription enzyme.
define a promoter
is the site where RNA polymerase binds to.
define the operator
is a place where the repressor binds.
define the repressor
binds to the operator and restricts RNA polymerase from coding the mRNA.
define genes (structural genes)
are what the RNA polymerase reads and creates mRNA molecules from.
When is the lac operon used?
lac operon- breaks down lactose- lactose is used when glucose is not present
what does the lac operon contain?
promoter, lac gene , and operator
What type of reaction is the lac operon and is it repressible or inducible
Inducible: normally off but can be turn on & catabolic reaction
what is a regulatory gene/ Lac I gene
lies upstream of the operon & has its own promoter (not part of the operon) & produces the repressor protein→ can toggle between active or inactive shape
What happens if there is no lactose- present
active repressors are bound to the operator and block them when no lactose is present
What does allolactose do?
binds to repressor & converts the repressor into the inactive form= removing the repressor from the RNA
what happened if there are low glucose levels and lactose is present?
Active CAP protein is trying to enhance transcription rate
cAMP binds to inactive CAP= active
→ active cap attaches to promoter & increases affinity of RNA polymerase to bind to the promoter & it enhances transcription rate
what happens if there is high glucose levels but lactose is present?
Don’t need lactose because glucose is available; glucose is easier to break down (monosaccharides) & its accessible
cAMP levels are low
Inactive lac repressor
RNA polymerase will still bind but the transcription rate will remain low
Where is the trp operon?
on the E.coli genome
What happens to the trp operon when tryptophan is abundant?
Tryptophan would bind to repressor so it binds to the operator& it would prevent RNA polymerase from translating the rest of the sequence
what happens to the trp operon when tryptophan is not abundant?
The trp repressor is inactive and is away from the operator when tryptophan is NOT in abundance in tWherhe environment.
RNA polymerase will continue coding for the tryptophan synthesis
Are trp operons repressible or inducible and are they catabolic/ anabolic?
Repressible operon- can become repressed
Anabolic reaction
