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Genetics > Virology2 > Flashcards

Virology2 Flashcards

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Biology 101 flashcards
1
Q

which viruses are naked icosahedral?

A

hepatitus A
polio viruses

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2
Q

which viruses are enveloped icosahedral?

A

yellow fever
herpes simplex
HIV

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3
Q

which viruses are enveloped helical?

A

influenza,
mumps,
measles,
rabies

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4
Q

which viruses are complex w many proteins (some combos of icosahedral & helical capsid structures) ?

A

herpesviruses
smallpox
hepatitis B
T4 bacteriophage

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5
Q

which viruses are circular?

A

papillomaviruses
many bacteriophages

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6
Q

which viruses is non-segmented?

A

parainfluenza viruses

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7
Q

which viruses are segmented?

A

influenza viruses

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8
Q

what is rolling-circle replication?

A

one strand of replicative form is nicked and replication enzymes are used to extend the free 3’ end

as complementary strand is synthesised around circular DNA, 5’ end is peeled off → displaced strand that continues to grow in length

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9
Q

what is viral reassortment?

definition + implication

A
  • the exchange of genetic material between segments of 2 (or more) viruses of the same strain that have coinfected the same cell
  • causes antigenic shift → increases pandemic potential

only in viruses w segmented genomes (flu, rota)

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10
Q

what is viral recombination?

A
  • exchange of genetic material between 2 chromos of similar/related strains that have coinfected a host cell
  • through crossing over of genes between 2 regions of homologous base sequences
  • results in progeny w genetic material from 2 paternal viral strains
  • increases genetic diversity
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11
Q

what is viral complementation?

A
  • 2 viruses coinfect host cell
  • virion A produces functional protein
  • virion B has mutation in genome → nonfunctional protein
  • no genetic info exchanged
  • functional protein used in progeny of both virions
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12
Q

what is phenotype mixing?

A
  • coinfection of cell w 2 related viruses
  • virus A genome is partially/completed coated by surface protein of virus B → pseudoviron formation (viral hybrid)
  • virus A determines genetic material of progeny
  • virus B proteins determine host tropism (infectivity of hybrid virus)
  • future generations lose this
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13
Q

what is phenotype masking (transcapsidation)?

A
  • related viruses infect same cell
  • capsid of 1 virus envelops genome of another virus
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14
Q

what is point mutation?

A
  • hemagglutinin or neuraminidase genes
  • causes antigenic drift → significantly increases potential of virus to cause epidemic
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15
Q

what are the 6 steps in a typical lytic cycle?

A
  1. attachment
  2. penetration
  3. uncoating
  4. replication & synthesis
  5. assembly
  6. release

APURAR

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16
Q

non-enveloped and enveloped viruses in the penetration step

A

non: via endocytosis or transmembrane transport

envelope: via endocytosis or fusion w host cell’s membrane

17
Q

what does the uncoating step of the lytic cycle refer to?

A

nucleic acid needs to be uncoating for virus replication to begin

18
Q

naked and enveloped during viral release stage

A

naked: released via cell lysis
enveloped: released via budding

budding doesn’t kill cells = persistent infections

19
Q

what is the difference in the viral life cycle between viruses with RNA and DNA genomes?

A

genome of RNA virus does not enter nucleus, everything happens in the cytoplasm (unlike DNA viruses)

20
Q

what are T-phages?

A

a series of seven phages that infect E.coli

21
Q

what are the T-even phages?

A
  • T2
  • T4
  • T6
22
Q

what are the dependent virulent T-phages?

A
  • T1
  • T3
  • T7
23
Q

which T-phage is autonomously virulent and which one is well-studied?

A

T5 → autonomously virulent
T4 → well-studied

24
Q

what are temperate phages?

A

become part of host chromo & replicated w cell genome until induced to make newly assembled viruses or progeny viruses

25
Q

what is the difference between lytic and lysogenic cycles?

ito of definition

A

lytic → virus destroys host cell (rapid process w lysis)
lysogenic → viral genomes becomes integrated into host genome

26
Q

describe the lysogenic cycle (5)

A
  • latent period: host cell not killed → viral nucleic acids undergo genetic recombination
  • bacterial DNA replicates = prophages replicate
  • lysogenic/phage conversion (change in phenotype)
  • persistin host until induction → excision of viral genome from host → proceed to lytic cycle
  • lysogeny
27
Q

provirus vs prophage

A

provise doesn’t undergo excision after splicing into genome

28
Q

what are the 4 symptoms of viral infection in plants?

A
  • hyperplasia = galls
  • hypoplasia/dec in cell growth = yellowing
  • cell necrosis = cell death
  • malformed leaves
29
Q

what are the 2 main courses of viral infection?

+ subdivisions

A
  1. acute
  2. persistent
    * latent infection
    * chronic infection → host cell infusion
    * transforming infection
30
Q

what is the course of a typical acute infection?

A

virus prod increases → reaches threshold level → adaptive response → clear infection → antibodies, residual effector cells & memory cells = protection

31
Q

what is persistent infection?

A
  • when virus not completely cleared from system of host but stays in certain tissues or organs of infected person
  • 2 main categories: latent & chronic
32
Q

what is latent infection?

A

virus remains in equilibrium with host for long periods before symptoms again appear, but actual viruses can’t be detected until reactivation of disease occurs

HSV, chicken pox

33
Q

what is slow infection?

A

slow virus period of a year separates the initial acute infection & fatal outcome

hep B

34
Q

what is chronic infection characterised by?

A

continued presence of infectious viruses following primary infection

35
Q

what are the 2 viruslike agents?

A

viroids → no coat proteins, infectious ssRNA
prions → infectious particles made of proteins, lack nucleic acid

Genetics (14 decks)

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