15 Questions
What is the major mechanism for controlling the production of a protein encoded by a given gene?
Transcriptional control
In unicellular organisms, genes are regulated to adjust to changes in which environments?
Nutritional and physical
Roughly half of the genes in E. coli are organized into what structures?
Operons
What must E. coli RNA pol associate with in order to initiate transcription?
σ70
What binds to the promoter of the lac operon?
σ70
What blocks the start site of transcription in the absence of lactose?
Lac repressor
What happens to transcription of the lac operon in the absence of lactose?
It is repressed
What releases the lac repressor from the operator sequence, de-repressing transcription?
Lactose
What is a better energy source than lactose for E. coli?
Glucose
What does E. coli synthesize in response to low glucose levels?
cAMP
What protein does cAMP bind to and activate?
CAP
What greatly stimulates the rate of transcription initiation by interacting with RNA pol?
CAP
In the presence of high tryptophan levels, what happens to the trp operon?
It is repressed
What are the major processes that regulate protein concentrations in eukaryotes?
Transcription, mRNA degradation, mRNA translation, and protein degradation
What controls cell protein concentration by gene transcription, mRNA degradation, protein translation, and protein degradation?
Cell protein concentration
Study Notes
Transcriptional Control in Prokaryotes and Eukaryotes
- E. coli RNA pol must associate with a sigma factor, commonly σ70
- σ70 binds to the promoter of the lac operon
- Lac repressor binds to the operator, blocking the start site when lactose is absent
- Transcription of the lac operon is repressed in the absence of lactose
- When lactose is present, it binds to the lac repressor, releasing it from the operator sequence and de-repressing transcription
- Glucose is a better energy source than lactose
- E. coli synthesizes cAMP in response to low glucose levels
- cAMP binds to and activates a transcriptional activator protein called CAP
- CAP interacts with RNA pol and greatly stimulates the rate of transcription initiation
- The trp operon is repressed in the presence of high tryptophan levels
- Cell protein concentration is controlled by gene transcription, mRNA degradation, protein translation, and protein degradation
- Major processes that regulate protein concentrations in eukaryotes include transcription, mRNA degradation, mRNA translation, and protein degradation
Test your knowledge of transcriptional control in prokaryotes and eukaryotes with this quiz. Explore key concepts such as RNA polymerase association, promoter binding, lac operon regulation, cAMP signaling, and protein concentration regulation.
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