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infectious agents 2 > Viral Replication > Flashcards

Viral Replication Flashcards

1
Q

Most DNA viruses replicate in the ________, most RNA viruses replicate in the _______

A

Cell nucleus; cytoplasm

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2
Q

What 2 DNA viruses replicate in the cytoplasm?

A
  • poxviridae

- African swine fever

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3
Q

What RNA viruses replicate in the nucleus?

A
  • orthomyxoviridae
  • retroviridae
  • some paramyxoviruses (canine distemper)
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4
Q

Replication cycle outline

A
  • attachment or adsorption
  • penetration or uptake
  • uncoating
  • synthesis of viral nucleic acid and protein
  • assembly/ maturation
  • release
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5
Q

Attachment/adsorption

A

Virus attaches to cell surface

  • occurs via ionic interactions (temp independent)
  • recognizes specific receptors on cell surface –> cells without receptors are not susceptible to the virus!
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6
Q

Penetration

A

Virus enters the cells

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7
Q

What are 2 ways enveloped viruses can enter cells?

A
  • fusion: entry via fusing with plasma membrane
  • endocytosis: entry by endosomes at the cell surface
  • -> virus taken up by invagination of clathrin-coated pits into endosomes
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8
Q

Endocytosis

A

Endosome becomes acidified –> virus membrane fuses with endosome membrane
- fusion of endosome and viral membrane = release of internal components of virus

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9
Q

Penetration for non-enveloped viruses

A

Virus crosses plasma membrane directly, or is taken up via clathrin-coated pits into endosomes
- virus directly crosses endosome membrane

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10
Q

Uncoating

A

Nucleic acid must be uncoated before virus replication can begin
- after uncoating, infectious virus particles cannot be recovered from cell (lasts until new infectious virions are made)

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11
Q

Assembly/maturation

A

Maturation may follow the initial assembly process
- viruses in final stage of assembly go thru a set of structural transitions and/or biochemical modifications that transform recursor particles into infectious particles

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12
Q

Release

A
  • cell lysis
  • budding (does not have to kill host cell)
  • not all released viral particles are infectious
  • enveloped viruses released by budding from plasma membrane
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13
Q

Structural protein

A

All proteins in a mature virus particles, even if they make no contribution to the morphology or rigidity of the virion

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14
Q

Non structural protein

A

Viral proteins found in the cell, but not packaged into the virion

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15
Q

How do viruses affect host cells?

A

Many inhibit host RNA, DNA or protein synthesis

- damage the function of cells or kills cells

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16
Q

Cytopathic effect

A

Morphological changes in the host cell caused by viruses

  • consist of cell rounding, disorientation, swelling/shrinking, death, detachment from the surface
  • depends on virus and cells on which it is grown
  • will take a couple of inoculations to see CPE on artificial media
17
Q

Use of CPE

A
  • identify virus isolate

- quantitate infectious virus particles by the plaque-forming unit

18
Q

Isolation and propagation of viruses

A
  • animals
  • embryos
  • cell cultures
19
Q

The more virus passes or adapts in host cells, the more _______

A

Virulence the virus becomes to the host

20
Q

Preparation of specimen for inoculation

A

Fresh or frozen tissues –> homogenize –> freeze and thaw (rupture cell/release virus) –> low speed centriguation and filtration –> spin down viruses with ultra speed centrifugation

21
Q

Primary culture

A

First in vitro cultures of cells taken directly from the organs
- requires death of animal hosts

22
Q

Cell line

A

Cell line that can be subcultured and grow continuously

  • ex: tumor cell that can be subcultured for many passages
  • do not need to kill host
23
Q

Growth of virus in cultured

A
  • choice of cultured cells
  • recognition of viral growth
  • growth of virus in lab animals
  • growth of virus in embryos-chicken embryonic eggs
24
Q

A virus contains DNA and RNA

A

False

25
Q

Viruses must have either double-stranded DNA or RNA

A

False

26
Q

All viruses have an envelope

A

False

27
Q

Viruses can be propagated in rich artificial media without cells

A

False

- cannot make proteins on their own

28
Q

Adenoviridae

A
  • site of replication: nucleus
  • eclipse period (hr): 10
  • budding (membrane): none
29
Q

Herpesviridae

A
  • site of replication: nucleus
  • eclipse period (hr): 4
  • budding (membrane): nuclear
30
Q

Poxviridae

A
  • site of replication: cytoplasm
  • eclipse period (hr): 4
  • budding (membrane): golgi
31
Q

Retroviridae

A
  • site of replication: nucleus
  • eclipse period (hr): 10
  • budding (membrane): plasma
32
Q

Only enveloped viruses can do _______, but both enveloped and nonenveloped viruses can do _________

A

Fusion; endocytosis

33
Q

Are all progeny created from replication infectious?

A

NO

- could be noninfectious due to mutations, etc

34
Q

You do not know if a virus is present within a cell without ______

A

CPE

- each virus has its own unique CPE

infectious agents 2 (29 decks)

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