Lecture 37 - Virology Intro Flashcards

1
Q

Do all viruses cause disease? If not, why not?

A

No - can be avirulent, not in primary host, latent infection, or host mechanisms stop disease symptoms

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2
Q

Define virome

A

all viruses in given environment (viral biome)

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3
Q

T/F: viruses outnumber bacterua 10:1 in most ecosystems

A

TRUE

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4
Q

What are the 3 theories of viral origin?

A
  1. self-replicating molecules that existed before cells
  2. evolved from genetic elements within cells that gained the ability to move between cells
  3. ancient intracellular parasites that lost other functions
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5
Q

what are the reasons that there are new viruses?

A
  1. mutations
  2. zoonoses development
  3. genetic shift
  4. recombination events
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6
Q

how do zoonotic viruses like SARS coronavirus spread to humans

A
  • emerge from bats
  • go to intermediate species in a new environment
  • infect humans in close contact
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7
Q

T/F: mosquitoes are a vector for many viruses

A

TRUE

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8
Q

what are the ways humans can be infected by zoonotic viruses

A
  1. bats to intermediate species
  2. mosquito-borne
  3. primates to humans
  4. food animal-borne
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9
Q

the spread of HIV or ebola virus to humans illustrates what kind of viral spread

A

between closely related animal species

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10
Q

what is viral genomics teaching us

A

viruses have always existed but we are recently finding them via technology

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11
Q

why are viruses considered infectious pathogens

A
  1. spread to other cells or hosts
  2. infection alters fundamental cell processes
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12
Q

what are the 4 steps of viral replication

A
  1. enter
  2. replicate
  3. exit
  4. spread
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13
Q

what two structures do viruses have that help replication

A
  1. nucleic acid genome
  2. protective coat
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14
Q

what do viruses lack?

A
  • functional ribosomes
  • mitochondria
  • means to generate metabolic building blocks
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15
Q

how can viruses be categorized

A

obligatory intracellular parasites

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16
Q

how are progeny viruses created (2 steps)

A
  1. synthesize viral components
  2. assemble
17
Q

define tropism

A

restricted site for viral replication

18
Q

what can viruses infect based on restrictions

A
  1. only one kingdom (animal, plants, fungi, Protista, bacteria)
  2. only one/several animal species
  3. a limited number of tissues and cell types
19
Q

to study viruses, what 4 things do we do in a laboratory

A
  1. isolate (swabs/sampling)
  2. amplify
  3. concentrate
  4. purify/enrich
20
Q

what does amplification select for

A

viral mutant in an unnatural/selective environment

21
Q

what are the advantages and disadvantages of using laboratory animals for amplification

A

advantages: natural environment does not select for adaptive mutations

disadvantage: no consent from animal, discomfort

22
Q

what are the advantages and disadvantages of using embryonated eggs for amplification

A

advantage: respiratory viruses grow well, sterile environment

disadvantage: most enteric viruses don’t grow in eggs, egg allergy

23
Q

what are the advantages and disadvantages of using organ cultures for amplification

A

advantage: grow viruses that don’t grow in cultures

disadvantages: difficult to maintain

24
Q

what are the advantages and disadvantages of using cell cultures for amplification

A

advantage: easy to amplify the virus

disadvantage: many viruses don’t grow in cultures, select adaptive mutations

25
Q

T/F: different viruses mutate at different rates

A

TRUE

26
Q

define strain

A

lines or isolates of the same virus

27
Q

define type

A

the same virus expresses different antigens or other molecules on their surface

28
Q

define variant

A

virus mutant that differs from wild-type strain in phenotype

29
Q

deletion or nonsense mutation

A

results in loss of protein expression needed for viral replication

30
Q

host range mutation

A

ability of virus to infect new host cell or species

31
Q

resistance mutations

A

virus adapts to antiviral drugs or host defense responses

32
Q

reverse mutations

A

virus returns to wild-type once drug or host defense pressure is removed