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MIMM 324 > 1. Intro to Virology > Flashcards

1. Intro to Virology Flashcards

1
Q

what do viruses infect?

A

all living things

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2
Q

how many virus particles do we encounter per day? how do virus particles outnumber cellular life?

A

billions!

outnumber cellular life 10:1

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3
Q

what has the greatest biodiversity on earth?

A

viruses

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4
Q

do we carry viral DNA?

how much of blood plasma DNA is viral?

A

yes, we carry viral DNA as part of our own genetic material

about 70% of DNA from blood plasma is viral

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5
Q

3 reasons why viruses are beneficial

A
  1. drive global cycles (i.e. catalyze movement of nutrients from organisms, kill 20-40% of ocean microbes, regulate earth’s ecology)
  2. transfer genes btwn organisms
  3. prevent and cure disease
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6
Q

what 7 things have viruses told us about cell biology?

A
  1. promoters for euk RNA pol
  2. DNA replication enzymes
  3. reverse transcriptase
  4. RdRP
  5. RNA splicing
  6. Translation
  7. Identification of oncogenes
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7
Q

what is a virus?

A

INFECTIOUS, OBLIGATE, intracellular parasite

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8
Q

what 2 things do viruses contain? what is one additional thing that viruses may contain?

A
  1. genetic material
  2. protein capsid coat

may have envelope from host cell membrane

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9
Q

why did we previously not realize that viruses could be large?

A

we used to identify viruses by filtering, so we did not see the larger viruses

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10
Q

what are the 2 phases of viruses?

A
  1. inanimate phase –> virion
  2. multiplying phase –> in infected cell
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11
Q

are viruses active or passive?

A

passive –> they don’t actually do anything

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12
Q

how were viruses first visualized?

A

electron microscopy

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13
Q

what are 4 ways that viruses are classified based on physical attributes?

A
  1. nature and sequence of nucleic acid virion
  2. symmetry of capsid
  3. presence/absence of envelope
  4. dimensions of virion and capsid
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14
Q

what are the 7 taxonomy classes?

A
  1. kingdom
  2. phylum
  3. class
  4. order
  5. family
  6. genus
  7. species
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15
Q

what is the suffix for the ORDER name of viruses?

A

-VIRALES

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16
Q

what is the suffix for the FAMILY name of viruses?

A

-VIRIDAE

17
Q

what is the suffix for the GENUS name of viruses?

A

-VIRUS

18
Q

what are the 7 steps of a virus infectious cycle?

A
  1. receptor binding
  2. entry and uncoating
  3. early gene expression
  4. replication of viral genome
  5. late gene expression
  6. assembly of virions
  7. exit
19
Q

describe RECEPTOR BINDING

A
  • virus-encoded proteins recognize and bind to cells at a receptor
20
Q

what can a viral receptor be made of?

A

protein, carbohydrate, lipid

21
Q

describe tropism

A

tropism = the type of cell a virus affects
determined by the receptor and replication machinery

22
Q

what are cellular receptors specific for?

A

specific for each virus and host species

23
Q

how do bacteriophages enter the cell?

A

they have tails that drill holes and then inject their genome into the host cell

24
Q

how do plant viruses enter the cell?

A

damage the cell wall then penetrate thru

25
Q

how do animal viruses enter the cell?

A

membrane fusion OR endocytosis

26
Q

what happens to a virus once it is inside the cell?

A

uncoating –> capsid disintegrates to release the genome

27
Q

describe EARLY GENE EXPRESSION

A

viral genome directs expression of early protein –> depends on type of genome

28
Q

describe REPLICATION OF VIRAL GENOME

A

early proteins promote replication of the viral genome –> allowing cell to become factory for expression and replication of viral genome

29
Q

describe LATE GENE EXPRESSION

A

late mRNA are made from newly replicated genomes to produce STRUCTURAL proteins (ex. glycoproteins from capsid proteins)

30
Q

are early or late proteins expressed in greater quantities?

A

LATE

31
Q

describe the ASSEMBLY OF VIRIONS

A

structural proteins package viral genomes and assemble the capsid

32
Q

what do enveloped viruses encode for the assembly of virions?

A

enveloped viruses encode glycoproteins that insert into lipid membranes to direct formation of viral envelope

33
Q

describe EXIT

A

virions released via:
A. death and lysis of host cell
B. budding from cell membrane to form envelope

34
Q

what do all viruses must make?

A

ALL viruses MUST make mRNA to be translated by host ribosomes

35
Q

why are viruses considered parasites?

A

parasites of the host protein synthesis machinery

36
Q

what is the strategy of viral propagation?

A

pre-form the components and then assemble into the final product

37
Q

describe viral propagation if all cells are infected

A

ECLIPSE PERIOD - no infectious particles, but virus is replicating, etc.

BURST/YIELD - release of virions

38
Q

describe viral propagation if a few cells are infected

A

there are more cells than virions so after the initial burst, neighbouring cells are infected and a second burst occurs

MIMM 324 (37 decks)

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