Bacterial Gene Expression Flashcards
What are the three elements of the Oberon?
The genes that it controls,
A promoter region where RNA polymerase first binds,
An operator region between the promoter and the first gene that acts as an “on-off switch”.
Where are operons commonly found?
Prokaryotes
What is an inducible operon?
an operon that does not continuously express it’s genes
can be expressed by a small molecule called an inducer
What is a lac operon?
Encodes enzyme for the metabolism of lactose in E. coli
Only expresses genes when glucose is ABSENT and lactose is PRESENT
What is the inducer molecule that aids in lac operon expression?
Allolactose
What are the three genes in a lac operon?
LacZ, lacY, lacA
What does the CAP site do?
binds to a region of DNA just before the lac operon promoter and helps RNA polymerase attach to the promoter, driving high levels of transcription.
What is the CAP site?
CAP site is a glucose sensor using a CAP protein molecule, which when bound expresses operon if no glucose present
What is the operator?
Operator is a lactose sensor. Usually blocks RNA pol to stop transcription, but if lactose is present it stops acting as a repressor
What does CAP stand for?
catabolite activator protein
What happens to lac operon when glucose levels are low?
cAMP is produced and attaches to CAP, making the CAP bind DNA
What happens when there’s high glucose levels?
No bound DNA so transcription occurs at low levels
What is a Trp operon?
Encodes enzymes for the synthesis of tryptophan in E. coli
When does the repressor bind to DNA to block transcription?
Only when tryptophan is present because the cell no longer has to make it
