Viruses and Prions Flashcards

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1
Q

viruses are

A

submicroscopic infectious particles

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2
Q

virus characteristics

A

acellular (no cells)
obligate intracellular pathogens
DNA or RNA
infect all known life
no metabolism

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3
Q

when were viruses discovered

A

1898

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4
Q

virus size

A

20 - 1000 nm long

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5
Q

virion

A

single infectious virus particle

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6
Q

virion parts

A

exterior protective protein capsid
genetic material

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7
Q

capsid

A

protein shell
bulk of a vision
capsomere subunits

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8
Q

animal viruses can be

A

helical
icosahedral
complex

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9
Q

bacteriophage

A

complex capsids
attach to cell surface to inject genetic material

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10
Q

envelope

A

lipid-based
arises from budding off host cell
animal viruses may be enveloped
bacteriophages are not enveloped

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11
Q

naked (nonenveloped)

A

viruses that lack an envelope
cell lysis (bursting)

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12
Q

spikes

A

peplomers
protrusions from capside or envelope
glycoproteins
aid in attachment and entry to host cell

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13
Q

glycoprotein

A

proteins with sugars

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14
Q

stages of animal virus replication

A
  1. attachment
  2. penetration
  3. uncoating
  4. replication
  5. assembly
  6. release
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15
Q

attachment

A

naked viruses attach to host cells using capsid proteins
other viruses use spike proteins

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16
Q

host range

A

collection of species a virus can infect

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17
Q

tropism

A

range of tissues or cells a virus can infect inside a given host
specificity - “lock and key”

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18
Q

penetration

A

enveloped - endocytosis or fusion
naked - endocytosis

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19
Q

uncoating

A

capsid is digested by enzymes

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20
Q

replication needs to do 2 things

A
  1. replicate nucelic acid
  2. produce new structural proteins
21
Q

DNA virus replication

A

replicates DNA and makes RNA
RNA produces viral proteins
proteins and new DNA make virions

22
Q

RNA virus replication

A

RNA makes new proteins
RNA-dependent RNA polymerase produced more RNA molecules
these work together to build new virion

23
Q

retrovirus (RNA)

A

reverse transcriptase to produce DNA
then follows DNA replication process

24
Q

assembly

A

formation of new virions
packaging of genome

25
Q

release

A

enveloped - budding
naked - lysis of host cell

26
Q

viral infection types

A

acute
chronic
latent
systemic

27
Q

acute infection

A

continuous viral replication

28
Q

chronic infection

A

slow release of viral particles
may or may not kill host cell

29
Q

latent infection

A

acute, but virus enters quiescent period (dormant)
no new viral progeny produced
reactivation

30
Q

systemic infection

A

in plants
the plant rarely recovers

31
Q

oncogenic viruses

A

causes ~ 10 - 15% of cancers
stimulate uncontrolled host cell division
decreases host cell responsiveness to death signals
ex. HPV

32
Q

what do bacteriophages infect

A

bacteria

33
Q

bacteriophage replication

A

lytic or lysogenic

34
Q

lytic replication pathway

A
  1. adsorption
  2. penetration
  3. replication
  4. assembly
  5. maturation
  6. release
35
Q

temperate phages

A

can be lytic or lysogenic (both are possible)

36
Q

lysogenic replication pathway

A
  1. adsorption
  2. penetration
  3. integration (cell division or lytic cycle entry)
  4. replication
  5. assembly
  6. maturation
  7. release
37
Q

integration

A

prophage - viral genes in host chromosomes

38
Q

prophage conversion

A

confer new pathogenicity factors to bacteria

39
Q

prions

A

infectious, misfolded proteins

40
Q

prion characteristics

A

no genetic material
do not replicate in classical sense
made from proteins most abundant in brain

41
Q

what do prions cause

A

transmissible spongiform encephalopathies

42
Q

prions in sheep cause

A

scrapie

43
Q

prions in cows cause

A

bovine spongiform encephalopathy (BSE)
“Mad Cow Disease”

44
Q

prions in humans cause

A

kuru (from cannabalism)
Creuzfeldt-Jakob disease (CJD)

45
Q

prions come from

A

PrPC (made by all mammals)

46
Q

prions form

A

amyloids - abormal aggregates

47
Q

infectious form on PrPC

A

PrPSc

48
Q

prion transmission

A

acquired - direct exposure
genetic - familial
sporadic - unknown (85% of cases)