Basic Transcription Part 3 Flashcards
1
Q
Lytic Phase
A
- infection
- phage DNA cyclizes
- decision point
- phage DNA replicates (rolling circle)
- phage heads, tails, and DNA assemble into progeny phages
- cell lysis
- reinfection
2
Q
Lysogenic Phase
A
- infection
- phage DNA cyclizes
- decision point
- integration of phage DNA
- cell division
- phage DNA replicates
- goes through lytic cycle
3
Q
Lysogenic mode
A
- early genes transcribed and translated by host
- lambda repressor binds 2 phage operons
- shuts down all other transcription (genes needed for lysis)
- phage integrates into host genome
4
Q
lysogen
A
- a bacterium contining integrated phage DNA
5
Q
prophage
A
- integrated phage DNA
6
Q
when lysogen encounters mutagenic chemicals
A
- phage can enter lytic cycle
7
Q
DNA
A
- linear in phage and circular soon after infection
- brings together all late genes that are separated when the phage is linear
8
Q
3 phases of transcription
A
- immediate early
- delayed early
- late
- 3 class arranged sequentially on phage DNA
9
Q
program of gene expression controlled by
A
- antitermination
- transcriptional switches
10
Q
immediate early genes
A
- PL - N
- PR- cro
11
Q
PL
A
- promoter to the left
12
Q
N
A
- antiterminator
13
Q
PR
A
- promoter to the right
14
Q
cro
A
- repressor of lambda repressor
15
Q
Delayed early genes for lysis
A
- Q antiterminator
16
Q
Q antiterminator
A
- permits transcription of late genes
17
Q
Delayed early genes for lysogeny
A
- CII and CIII lead to CI expression
18
Q
late genes
A
- only transcribed when cell will undergo lysis
- not when phage integrates
19
Q
immediate early genes
A
- host RNA polymerase binds PR and PL
- transcribes immediate early genes first
20
Q
two immediate early genes
A
- cro
- N
- transcribed from PR and PL
21
Q
polymerase encounters what when transcribing immediate early genes
A
- rho-dependent terminators
- encounters before delayed early genes
22
Q
delayed early genes
A
- cro repressor blocks transcription of lambda repressor genes
23
Q
lambda repressor gene
A
- CI
- located between two promoters
24
Q
N antiterminator
A
- causes RNA polymerase to ignore terminators and transcribe delayed early genes
25
same promoters are used for
- immediately and delayed early gene expression
26
delayed early genes are important to
- continue lytic cycle
| - establish lysogeny
27
Genes O and P for lysis
- Genes O and P code for proteins needed for phage DNA replication
28
late genes
- all transcribe in rightward direction
- not from PR
- proteins that make up phage head and tail
- proteins that lyse host cell
29
late promoter
- PR'
| - located just downstream of Q
30
in absence of Q
- transcription of from PR' terminates after 194 bases
31
N+Q
- anti terminators
| - work via a different mechanism
32
Two delayed early genes help establish lysogeny
- some needed for integration of phage DNA into host genome - prerequisite for lysogen
- products of cII and cIII genes allow transcription of cI gene = lambda repressor
33
lambda repressor
- central component in lysogeny
| - repressor of lysis
34
anti termination by N
- N is immediate early gene
35
in absence of N
- transcription from PL produces N and termination occurs downstream
36
N protein binds
- the N transcript at the N utilization site
- binds to its own transcript
- allows polymerase to go through rho-dependent terminator and continue on and allow readthrough
37
nut site
- contains an inverted repeat
- probably forms a stem loop
- RNA must loop out
38
processive
- anti termination factors remain associates with polymerase as it moves down DNA
- not terminated
39
lambda phage
- virus that infects E. coli cell
