Basic Transcription Part 3 Flashcards Preview

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Flashcards in Basic Transcription Part 3 Deck (39):
1

Lytic Phase

- infection
- phage DNA cyclizes
- decision point
- phage DNA replicates (rolling circle)
- phage heads, tails, and DNA assemble into progeny phages
- cell lysis
- reinfection

2

Lysogenic Phase

- infection
- phage DNA cyclizes
- decision point
- integration of phage DNA
- cell division
- phage DNA replicates
- goes through lytic cycle

3

Lysogenic mode

- 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

lysogen

- a bacterium contining integrated phage DNA

5

prophage

- integrated phage DNA

6

when lysogen encounters mutagenic chemicals

- phage can enter lytic cycle

7

DNA

- linear in phage and circular soon after infection
- brings together all late genes that are separated when the phage is linear

8

3 phases of transcription

1. immediate early
2. delayed early
3. late

- 3 class arranged sequentially on phage DNA

9

program of gene expression controlled by

- antitermination
- transcriptional switches

10

immediate early genes

- PL - N
- PR- cro

11

PL

- promoter to the left

12

N

- antiterminator

13

PR

- promoter to the right

14

cro

- repressor of lambda repressor

15

Delayed early genes for lysis

- Q antiterminator

16

Q antiterminator

- permits transcription of late genes

17

Delayed early genes for lysogeny

- CII and CIII lead to CI expression

18

late genes

- only transcribed when cell will undergo lysis
- not when phage integrates

19

immediate early genes

- host RNA polymerase binds PR and PL
- transcribes immediate early genes first

20

two immediate early genes

- cro
- N
- transcribed from PR and PL

21

polymerase encounters what when transcribing immediate early genes

- rho-dependent terminators
- encounters before delayed early genes

22

delayed early genes

- cro repressor blocks transcription of lambda repressor genes

23

lambda repressor gene

- CI
- located between two promoters

24

N antiterminator

- 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