Unit 3: Regulating Transcription in Prokaryotes Flashcards
MCB 181R University of Arizona
How does regulating gene expression in prokaryotes compare to eukaryotes?
It is simpler in prokaryotes because:
- Prokaryotic DNA is not packaged into chromatin.
- Prokaryotic mRNA is not processed.
- There is no nuclear membrane separating transcription and translation.
Where does transcription and translation occur in prokaryotes?
Cytoplasm.
What are the general ways prokaryotic cells regulate gene expression?
- Whether and how much a gene is transcribed.
- Whether and how much an mRNA is translated
- mRNA stability (how long it lasts).
- How proteins are processed (which affects their activity/function).
What regulates prokaryotic gene transcription?
Proteins that bind to DNA sequence.
Can transcription be regulated positively or negativity in prokaryotes?
Yes.
What do prokaryotes and eukaryotes have in common regarding transcription regulation?
Transcription can be positivity or negatively regulated.
Does transcibing a naked gene in prokaryotes require trnsciption factors?
No.
How efficient is transcription of naked gene in prokaryotes often?
Often NOT very efficient.
What kind of special non- coding regulatory sequences can genes have in prokaryotes?
Sequences that can be bind to activator proteins or repressor proteins.
How do these regulatory sequences in prokaryotes compare to those in eukaryotes?
Their effect is basically the same as silencers and enhancers in eukaryotes.
What is a key difference in the location of these regulatory sequences between prokaryotes and eukaryotes.
In prokaryotes, these sequences are usually close to the gene.
What happens when an activator protein binds to a non-coding regulatory sequence? (Positive Regulation)
The bound activator protein helps bring RNA Polymerase to the gene’s transcription of the gene.
What is the DNA sequences that an activator protein binds to often named after?
The specific type of activator protein that binds to it.
What is another kind of non-coding regulatory sequence in prokaryotes? (Negative Regulation)
An operator.
What can an operator bind to?
A repressor protein.
What happens when a repressor protein is bound to the operator?
The bound repressor protein blocks the RNA polymerase from getting to the gene, so it “turns off’ transcription of the gene.
How does a repressor protein physically prevent transcription?
It physically blocks RNA polymerase from getting to the gene to transcribe it.
What happens if both an activator and repressor are bound to their respective sequences for a gene?
The repressor wins, and the gene will NOT be transcribed at high levels.
What does the existence of different activator and repressor proteins allow for?
This allows different genes to be regulated separately.
Can activator and repressor proteins be regulated by molecules that bind to them?
Yes.
In some cases, how can a molecule binding to a regulatory protein affect its DNA binding?
A molecule can be bind to the protein to allow the protein to bind the DNA.
Define allosteric regulation of a protein.
When a molecule binds to one part of a protein and affects the function of another part of the protein.
Give an example of allosteric regulation mentioned in the notes.
Molecular binding to repress or activator proteins to allow or prevent them form binding DNA.
How is transcription regulated in prokaryotes, similar to eukaryotes?
There are different “flavors” of activator proteins and repressor proteins, and the sequences that they bind to. This allows different genes to be regulated separately.
