1
Q
Prokaryotic negative regulation
A
- Competition between RNA polymerase & repressor protein for promoter binding
2
Q
Prokaryotic Positive Regulation
A
- Activator protein recruits RNA polymerase to the promoter to activate transcription
3
Q
Where can prokaryotic gene regulatory elements be found?
A
- Close to transcriptional start site
- Far upstream of gene
- Downstream of gene (eukaryotes)
- Within gene (introns; eukaryotes)
4
Q
2 states of bacteriophage lambda in bacteria
A
- Prophage pathway
- Lytic pathway
5
Q
Prophage pathway
A
- Integrate lambda DNA into host chromosome
- Then it replicates with the DNA included
- Integrated lambda DNA replicates along with host chromosome
6
Q
Lytic Pathway
A
- Viral proteins synthesized to form a new virus
- Lambda DNA rapidly replicates into complete viruses
- Cell lysis releases a large number of new viruses to infect new bacteria
7
Q
Which 2 gene regulatory proteins are responsible for initiating the switch between prophage & lytic pathways?
A
- Lambda repressor protein
- Cro protein
8
Q
Lambda repressor (cI) - prophage state
A
- Blocks synthesis of Cro
- Activates its own synthesis
- Most bacteriophage DNA not transcribed (virus just along for the ride)
9
Q
Cro - lytic state
A
- Blocks synthesis of lambda repressor
- Allows its own synthesis by blocking repressor (doesn’t actively recruit RNA polymerase)
- Most bacteriophage DNA extensively transcribed (virus replicates)
10
Q
Which environment favours lytic vs. prophage states?
A
- Lytic: harsh environments, DNA damage
- Prophage: good growth conditions (positive feedback loop)
11
Q
4 types of transcriptional circuit loops
A
- Positive feedback loop
- Negative feedback loop
- Flip-flop device
- Feed-forward loop
12
Q
Positive feedback loop
A
- Create cell memory
- Makes more of itself (self-sustaining)
13
Q
Feed-forward loop
A
- Responds only to long signals
- Both A & B required for transcription of Z
14
Q
Repressilator
A
- Gene oscillator using delayed negative feedback circuit
- Each repressor regulates a different other one (A turns off B, turns off C, etc)
15
Q
Circadian Gene Regulation - Feedback loop
A
- Negative feedback loop in humans
- Repression of Tim & Per at night, then they accumulate over 24 hrs, then move from cytosol to nucleus & turn off their own expression.
16
Q
Transcriptional Attenuation
A
- Premature termination of transcription
- RNA adopts a structure that interferes with RNA polymerase, regulatory proteins bind to RNA and interfere with attenuation
17
Q
Riboswitches
A
- short RNA sequences that can change confirmation when bound by a small molecule
- Promote transcription attenuation
18
Q
Purine biosynthesis riboswitch
A
- Low guanine levels (low purines) = transcription of purine biosynthesis genes is on
- High guanine levels (high purines) = guanine binds riboswitch, riboswitch undergoes conformational change & causes RNA polymerase to terminate transcription, transcription of purine biosynthetic genes is off
BIO230 Part 1
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