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GN 421 > Basic Transcription Part 3 > Flashcards

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
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2
Q

Lysogenic Phase

A
  • infection
  • phage DNA cyclizes
  • decision point
  • integration of phage DNA
  • cell division
  • phage DNA replicates
  • goes through lytic cycle
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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
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4
Q

lysogen

A
  • a bacterium contining integrated phage DNA
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5
Q

prophage

A
  • integrated phage DNA
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6
Q

when lysogen encounters mutagenic chemicals

A
  • phage can enter lytic cycle
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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

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8
Q

3 phases of transcription

A
  1. immediate early
  2. delayed early
  3. late
  • 3 class arranged sequentially on phage DNA
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9
Q

program of gene expression controlled by

A
  • antitermination

- transcriptional switches

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10
Q

immediate early genes

A
  • PL - N

- PR- cro

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11
Q

PL

A
  • promoter to the left
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12
Q

N

A
  • antiterminator
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13
Q

PR

A
  • promoter to the right
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14
Q

cro

A
  • repressor of lambda repressor
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15
Q

Delayed early genes for lysis

A
  • Q antiterminator
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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
Q

same promoters are used for

A
  • immediately and delayed early gene expression
26
Q

delayed early genes are important to

A
  • continue lytic cycle

- establish lysogeny

27
Q

Genes O and P for lysis

A
  • Genes O and P code for proteins needed for phage DNA replication
28
Q

late genes

A
  • all transcribe in rightward direction
  • not from PR
  • proteins that make up phage head and tail
  • proteins that lyse host cell
29
Q

late promoter

A
  • PR’

- located just downstream of Q

30
Q

in absence of Q

A
  • transcription of from PR’ terminates after 194 bases
31
Q

N+Q

A
  • anti terminators

- work via a different mechanism

32
Q

Two delayed early genes help establish lysogeny

A
  • 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
Q

lambda repressor

A
  • central component in lysogeny

- repressor of lysis

34
Q

anti termination by N

A
  • N is immediate early gene
35
Q

in absence of N

A
  • transcription from PL produces N and termination occurs downstream
36
Q

N protein binds

A
  • 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
Q

nut site

A
  • contains an inverted repeat
  • probably forms a stem loop
  • RNA must loop out
38
Q

processive

A
  • anti termination factors remain associates with polymerase as it moves down DNA
  • not terminated
39
Q

lambda phage

A
  • virus that infects E. coli cell

GN 421 (36 decks)

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