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Virology > Lecture 4: virus replication cycle > Flashcards

Lecture 4: virus replication cycle Flashcards

1
Q

describe the infectious virus replication cycle

A

begins at attachment of single virus particle
virus enters and genome is replicated then assembly
ends in release of many virions from cell by lyses

replication length varies
all events inside single infected cell

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2
Q

describe animal cell culture

A

not possible before 1949
poliovirus first
primary cells are used
-animals tissue (embryonic/ newborn/ foreskin)
-express contact inhibition
-cells have finite lifetime (one time use)

mice liver tissue extracted and digested with collagenase

  • filter and obtain pellet
  • wash pellet- differential centrifugation
  • least dense (upper part) is added to culture enriched for slowly sedimenting single cells (primary cells form monolayer)
  • more dense (pellet) added to culture for dense cell clumps
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3
Q

maintain diploidy
~100 divisions (DNA shortens)
human embryos
can be harvestes

A

diploid cell lines

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4
Q 
aneuploid
indefinite growth
tumor tissue/ mutagens
atypical
can make own telomerase enzyme
grow over eachother
A

continuous cell lines

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5
Q

advantages and disadvantages of live animal models

A

advantages

  • only means until 1930s
  • essential for some viruses (need host not cell culture)
  • virus pathogenesis

disadvantages

  • inconvenient and expensive
  • variable responses
  • mutants
  • animal welfare issues
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6
Q

chorioallantoic membrane inoculation viruses in embryonic eggs

A

herpes simplex, poxvirus, rous sarcoma virus

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7
Q

amniotic inoculation viruses in embryonic eggs

A

influenza, mumps

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8
Q

yolk sac inoculation viruses in embryonic eggs

A

herpes simplex

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9
Q

allantoic inoculation viruses in embryonic eggs

A

influenza, mumps, newcastle disease, avian adenovisus

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10
Q

describe bacterial virus plaque assay

A

ellis and delbruck (1939)

  • infect lawn of bacteria
  • phage lyse host cell
  • quantitative
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11
Q

describe animal virus plaque assay

A

dulbecco (1952)

  • cultured cells form monolayer
  • localized infection of neighboring cells= plaque
  • staining necessary to visualize plaques (neutral red)
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12
Q

how many viruses needed to form a plaque

A

one hit (linear) kinetics

  • number of plaques directly proportional to first power of [ ] virus is inoculated in
  • if [ ] doubles then number of plaques doubles too
two hit (curved) kinetics
-number of plaques directly proportional to the square of    [ ] of the virus inoculated
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13
Q

-# of infectious particles added per cell
-infection depends on random collision of virions and cells
susceptible cells may remain uninfected or get one or more particles

A

MOI

multiplicity of infection

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14
Q

all cells infected at same time

A

synchronous infection

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15
Q

why use high inoculum dose

A
  • damage particles
  • defective genomes
  • “empty” capsids
  • antiviral properties
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16
Q

general stages of one step growth curve

A 
attachment/penetration
eclipse
-uncoating- releasing genome
-no progeny virus
latent
-intracellular virions
maturation
release
-extracellular virions
17
Q

step by step process of one step growth curve

A
  1. infect monolayers of tissue culture cells and allow infection to proceed in a CO2 incubator
  2. monitor experiments via inverted microscope
  3. collect infected cell lysates at various time points after infection
  4. perform serial dilutions on infected cell lysates and do plaque assay
  5. stain and analyze plaque assays. record results
18
Q

starts when virus detected

produce another virus in cells

A

eclipse

19
Q

typical virus replication cycle

A
  1. attachment- recognition and adsorption
  2. penetration- entry
  3. uncoating- disassembly and localization
  4. replication- transcription, translation, processing, duplication
  5. assembly
  6. maturation
  7. release
20
Q

typical virus replication cycle

A
  1. attachment- recognition and adsorption
  2. penetration- entry
  3. uncoating- disassembly and localization
  4. replication- transcription, translation, processing, duplication
  5. assembly
  6. maturation
  7. release
21
Q

how does a virus attach to host cell

A

-host cell surface receptors (essential)
-viral surface ligands (produced by virus)
proteins and glycoproteins

22
Q

ability to infect animal/cell culture

A

host range

23
Q

binding forces associated with interaction of cell receptors

A

electrostatic- form randomly and initial low affinity

hydrophobic- conformational changes and higher affinity

24
Q

binding forces associated with interaction of cell receptors

A

electrostatic- form randomly and initial low affinity

hydrophobic- conformational changes and higher affinity

25
Q

particle surrounded by plasma membrane and brought into cell
doesn’t happen with viruses
1-2um

A

phagocytosis

26
Q

describe plasma membrane fusion entry

A

receptor mediated
glycoproteins attach to receptors on membrane
fusion of viral and cellular envelope
nucleocapsid released inside cell
viral envelope forms patch on plasma membrane
-viral glycoproteins from virus left on membrane (how we know someone has a virus)

27
Q

describe plasma membrane fusion entry

A

receptor mediated
glycoproteins attach to receptors on membrane
fusion of viral and cellular envelope
nucleocapsid released inside cell
viral envelope forms patch on plasma membrane
-viral glycoproteins from virus left on membrane (how we know someone has a virus)

28
Q

always recycling- virus takes advantage
lowers pH- virus rely on it
always with receptor mediated transport

A

endosomes

29
Q

describe receptor mediated endocytic entry of enveloped virus

A
  • cathrin coated pit forms; triggered by virion-ligand cell surface receptor interaction
  • endocytic vesicle forms and becomes acidified
    • pumping H+ ions in, converting ATP to ADP
  • partial degradation of virion and potential expression of processed antigen
  • cathrin released virion partially ‘‘opened’’
  • capsid degraded and viral mRNA released in cytoplasm
30
Q

how are endosomes transported

A

along microtubules

Virology (15 decks)

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