Gene Expression Flashcards
Constitutive gene expression?
When genes are not under any control. Constitutive: having the power to establish or give organized existence to something:
Basal Transcription?
A minimal amount of transcription until it reaches the operon where regulation stops transcription.
What is the only way to have absolute zero transcription?
When the promotor is destroyed.
Environmentally regulated gene expression?
If the environment controls transcription.
Logic of gene regulation?
Cells don’t waste energy making proteins that they don’t need.
Where in the DNA strand is the operator located?
Upstream or downstream the promotor but right next to it; sometimes overlap.
Positive regulation?
•regulator protein binds to an operator and increases transcription. That protein is called the activator.
Negative regulation?
•A regulator that binds to the operator but decreases transcription.
How does positive regulation work?
The activator that needs to be there first helps sigma bind to the promotor.
How does negative regulation work?
A normal situation with sigma, but the repressor blocks RNA polymerase from proceeding.
Operon?
A set of coding regions that share the same promotor and terminator, even though they code for more than one genes.
Signals (inducers) can either to transcription?
Increase transcription.
Some repressors are expressed how?
Constitutive before the operon.
LacZ?
Degrades lactose to form glucose and galactose.
LacY?
A protein channel that pumps lactose into the cell by facilitated diffusion.
Allosteric enzyme?
When the substrate binds other than the active site which could possibly change the shape of the enzyme.
Why are repressors not completely attached to the operator?
Repressors use non-covalent interactions with DNA, and thee interactions are not permanent.
Mal operon?
Set of genes that allow bacteria to break down maltose into two glucose molecules.
How many proteins does the Mal operon code for? (3•)
•Two, •MalP, •MalQ
The role of MalP and MalQ?
Both of them are used to break down maltose.
Type of regulation of Maltose operon?
Positive regulation
Repressor for the Maltose Operon?
MalT
Is the repressor of Maltose functional once expressed?
No, they are folded.
How does an inducer help transcription?
It makes a weak promotor act like a strong by helping the sigma factor bind to the promotor.
Co-repressor?
A signal that causes transcription to go down, like tryptophan.
Anabolic-based (synthesis)?
Transcribe genes when the cells need more of whatever the proteins make.
Steps for determining the type of operon?
•If the operon undergoes positive or negative regulation: look at the strength of the promotor.
