Lecture 7 Flashcards
1
Q
Tryptophan operon regulation in Bacillus subtilis:
3
A
- Alternate, mutually exclusive stem-and-loop structures in the mRNA lead to termination or anti-termination
- High tryptophan leads to TRAP forming (C&D) resulting in anti-termination
- antiTRAP protein binds to inactivate TRAP, regulated by uncharged tRNAtrp
2
Q
Regulation of gene expression is mediated by
4
A
- Positive/negative
- DNA-binding/RNA binding
- Regulating transcription initiation/termination
- Most are regulated by an effector molecule having an allosteric effect on the conformation and activity of the protein
3
Q
Riboswitches influence gene expression in eukaryotes (some in fungi and plants) by..
(4)
A
- Altering the structure in the mRNA through the binding of an effector molecule, influencing gene expression by..
- Transcription termination (attenuation)
- Translation initiation
- No regulatory protein involved
4
Q
Alternative structures of riboswitches
2
A
- The normal confirmation does not result in transcription termination, but upon binding by an effector molecule
- A change in confirmation results in transcription termination
5
Q
Riboswitch example:
2
A
- SAM is a small effector molecule that binds when there is enough in the cell.
- When not bound 2&3 bind, but when bound 1&2 pair and 3&4 pair and termination follows
6
Q
Other riboswitches examples:
6
A
- Coenzyme B12
- Guanine
- Lysine
- Adenine
- Thyamine
- Flavin
7
Q
Bacteriophage lambda:
2
A
- A simple model organism
- Temperate bacteriophage of E.coli
- Lysis or lysogeny are the binary outcomes based on regulatory events of genes
8
Q
The Lambda life cycle:
A
- Infection of a cell
- 50kb linear genome circularises via cohesive sticky ends within the cell
- Either lytic growth (phage infects cell and replicates new phage, cell burst etc)
- OR lysogenic growth ohage
9
Q
The Lambda lytic pathway:
A
- Phage infects cell
- 50kb genome circularises using sticky ends
- DNA replicates using host machinery
- Cells lyses and lambda infects new cells
10
Q
The lambda lysogenic pathway
A
- Phage infects cell
- 50kb genome circularises using sticky ends
- DNA integrates into the cell chromosomes and lambda repressor is expressed
- Replicates with cell machinery until the repressor is turned off
- lysis follows
11
Q
Induction
A
- The lysogen is induced into the lytic cycle
- Often occurs under host cell stress
12
Q
Lambda genome parts:
7
A
- Cos sticky ends circularise
- Head protein genes
- Tail protein genes
- Lysis genes for breaking open the cell
- Integration and excision of E.coli
- DNA replication genes
- Regulatory functions
13
Q
Phage lytic development involves:
A
- A cascade of gene expression from early to middle to late genes
- New phage RNAP, sigma factors, promoters and anti-termination factors are used to progress to the next stage of gene expression
14
Q
Early genes:
A
- Phage genes are transcribed by host RNA polymerase
15
Q
Middle genes:
A
- Early product causes transcription of middle genes
16
Q
Late genes:
A
- Middle product allows transcription of late genes containing phage components
17
Q
Early genes are divided into two groups: Immediate early genes encode:
A
- Are transcribed by host RNAP from PL and PR
- cro from PL = negative regulator
- N from PR= antiterminator, which allows transcripts to extend into delayed early genes
18
Q
Early genes are divided into two groups: delayed early genes encode:
A
- Transcription initiates at PR and pQ
- cII/cIII = regulators, using 7 recombination genes and 2 replication genes
- Q = anti-terminator, allow transcripts to extend into late genes
19
Q
Late genes:
A
- 10 head genes
- 11 tail genes
- 2 lysis genes
20
Q
cIII
A
- maintains cII
- used in lysogeny
21
Q
N
A
- anti-terminator
- Turns on delayed early genes
- used in lysogeny and lysis
22
Q
cI
A
- lysogenic repressor
- lysogeny
23
Q
cro
A
- negative regulator
- turns off repressor
- lysis
24
Q
cII
A
- turns on repressor
- lysogeny
25
Q
Q
A
- anti-terminator
- turns on late genes
- used in lysis
26
Q
The promoters for the lytic cycle are
A
- PL
- Pr
- PR’
