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MicroBiology > Ch 6 > Flashcards

Ch 6 Flashcards

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1
Q

virus goal

A

infect host cells and exploit them to form new virions

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2
Q

which taxonomic domains are susceptible to viruses?

A

all domains

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3
Q

discovery of viruses began with

A

ivanovsky & beijerinck with the tobacco mosaic virus and “non-filterable particles”

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4
Q

size of viruses

A

20-900 nanometers / 0.02-0.9 micrometers

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5
Q

are viruses composed of cells?

A

no; they are obligate intracellular parasites

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6
Q

all viruses consist of ______

A

nucleic acids in a protein shell -> a capsid composed of repeating protein subunits, capsomeres

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7
Q

what is the virus protein shell called?

A

a capsid; composed of repeating protein subunits - capsomeres

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8
Q

can viruses self-replicate?

A

no; they must infect a host cell to reproduce
-they subvert the cell’s machinery and direct it to produce viral particles

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9
Q

what does virus utilize from host

A

-DNA polymerase*
-RNA polymerase*
-ribosomes
-tRNA’s
-nucleotides

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10
Q

steps after viral genome enters cell

A
  1. make copies of genome
  2. transcribe & translate viral genes
  3. viral proteins
  4. assemble virions
  5. exit host
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11
Q

each species of virus infects a particular group of species, or ______

A

host range

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12
Q

example of broad range virus

A

rabies

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13
Q

example of narrow range virus

A

HIV; only infects humans

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14
Q

name for animal viruses with tissue specificity

A

tropism

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15
Q

examples of tropism

A

broad -> ebola
narrow -> cold virus; HIV (infects T helper cells)

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16
Q

what type of tissue does coronavirus infect?

A

epithelial cells; membrane receptor expressed on the surface of airway epithelial cells

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17
Q

symmetrical viruses feature a

A

icosahedral or filamentous capsid

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18
Q

how does simplicity of capsid structure in symmetrical viruses affect the number of genes?

A

it minimizes the number of genes

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19
Q

enveloped viruses have

A

an envelope that surround the capsid; derived from the host membrane

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20
Q

“naked” viruses

A

lack envelopes

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21
Q

glycoprotein spikes function

A

host recognition & attachment, etc.
ex: herpesvirus, adenovirus

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22
Q

viruses with glycoprotein spikes include

A

herpesvirus and adenovirus

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23
Q

filamentous viruses properties

A

the capsid is a long tube of protein (varying length) with genome coiled inside

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24
Q

filamentous viruses examples

A

M13
Ebola
Tobacco Mosaic Virus

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25
Q

Tailed viruses add a _________ to the icosahedral head

A

genome delivery device

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26
Q

T4 bacteriophages have what kind of fibers

A

helical “neck” & tail fibers

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27
Q

asymmetrical viruses lack

A

capsid symmetry

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28
Q

symmetry of influenza viruses

A

Asymmetrical

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29
Q

Coronavirus properties

A

-nucleocapsid proteins
-enveloped viruses

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30
Q

Genome of Zika Virus

A

-non-segmented, single-stranded, (+) RNA genome
-10,794 bp long

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31
Q

influenza virus genome

A

-segmented, single-stranded (-) RNA genome; 8 segments
-11 proteins encoded; 13,500 bp total

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32
Q

viroids definition

A

RNA molecules without a capsid surrounding the RNA

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33
Q

what do viroids infect

A

plants

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34
Q

Are viroids viruses?

A

NO

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35
Q

sizes of small and large viruses

A

small: less than 10 genes
large: more than 100 genes

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36
Q

properties of viroids

A

-replicated by host RNA polymerase
-RNA does NOT encode for proteins; 300-400 NT long
-some have catalytic ability

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37
Q

effect of viroids

A

alter gene expression in affected plants

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38
Q

Prions definition

A

proteins that infect animals; NO nucleic acid component
-misfolded form of a normal brain cell protein

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39
Q

prions convert

A

a normal protein into the prion version, creating a chain reaction and producing a harmful aggregate in the cell

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40
Q

prions can cause

A

-degenerative brain diseases; creutzfield-jacob disease in humans; scrapie

41
Q

how are prions transmitted

A

in food prepared from infected animals; highly resistant to physical and chemical agents

42
Q

prion step-by-step invasion

A
  1. nerve cell makes normal PrP proteins
  2. Prion version of PrP invades, forcing normal PrP to refold into a prion form
  3. Unlike normal PrP, prions aren’t naturally destroyed by the cell. They accumulate, eventually killing it
  4. Prions move on to other cells and the cycle begins again
43
Q

viral ecology

A

important roles in ecosystems; limits host population densities; recycle nutrients; increase host diversity; gene transfer

44
Q

viral shunt

A

viral infection of hosts convert them to detritus, rich in organic & inorganic molecules

45
Q

check if we need to know mimivirus and pithovirus

A

unclear

46
Q

international committee on taxonomy of viruses based on

A

-genome
-capsid symmetry
-envelope
-host range
-virion size

47
Q

baltimore classification

A

-genome (RNA or DNA) & route used to express mRNA

48
Q

+RNA = mRNA =

A

“sense” RNA

49
Q

Group I viruses

A

dsDNA -> +mRNA

50
Q

Group II viruses

A

(+)ssDNA -> dsDNA -> +mRNA

51
Q

Group III viruses

A

dsRNA -> +mRNA

52
Q

Group IV viruses

A

(+)ssRNA -> (-)RNA -> +mRNA

53
Q

Group V viruses

A

(-)ssRNA -> +mRNA

54
Q

Group VI retroviruses

A

(+)RNA -> (-)DNA -> dsDNA -> +mRNA

55
Q

Groups 3, 4, 5 use

A

RNA dependent RNA polymerase (RDRP)

56
Q

reverse transcriptase is used in which group

A

Group VI retroviruses

57
Q

do we need to know all the virus examples in baltimore classification

A

thats like 22 viruses

58
Q

all viral life cycles comprise these events

A
  1. host recognition & attachment
  2. genome entry
  3. synthesis & virion assembly
  4. exit & transmission
59
Q

host recognition & attachment occurs via ______ to host cell surface proteins or glycoproteins

A

-recognition/binding of viral capsid proteins
-envelope proteins
-glycoproteins

60
Q

in genome entry, the entire capsid + genome ____

A

enters host cell (or only the genome may enter)

61
Q

synthesis and virion assembly involves

A

-genome replication
-proteins synthesis
-assembly of virions

62
Q

what happens in exit & transmission

A

release from host cell -> progeny infect more host cells

63
Q

the lytic cycle and lysogenic cycle are

A

bacteriophage life cycles

64
Q

lytic cycle

A

-T even phages
-phage quickly replicates

65
Q

lysogenic cycle phage type

A

-lambda phage; temperate phages

66
Q

which bacteriophage cycle kills the host quicker

A

lytic cycle - kills host immediately; lysogenic cycle does not necessarily kill host right away

67
Q

in lysogenic cycle, the phage integrates into the cell chromosome as a _______

A

prophage (site-specific recombination)

68
Q

lysogenic cycle phages can ______ to become ______

A

reactivate;
lytic

69
Q

what dictates when lysogeny converts to the lytic cycle

A

environmental cues /
the health of the cell

70
Q

“virulent” phages only carry out which cycle

A

lytic cycle (T4)

71
Q

temperate phages cycle between

A

lysis and lysogeny (e.g. lambda phage

72
Q

slow release bacteriophages ->

A

M13 filamentous phage (ssDNA)

73
Q

M13 phage particles reproduce and ____

A

exit without harming the host cell which grow slowly but don’t die

74
Q

types of bacterial host defenses

A

-genetic resistance
-restriction endonucleases

75
Q

how does genetic resistance work as a host cell defense

A

receptor proteins are altered

76
Q

how does restriction endonuclease work as a host cell defense

A

by cleaving viral DNA sequences lacking methylation

77
Q

bacterial DNA is methylated on the

A

cytosine nucleotides

78
Q

CRISPR stands for

A

Clustered Regularly Interspaced Short Palindromic Repeats

79
Q

in CRISPR, host cleaves phage DNA and inserts

A

fragment into chromosome as a “spacer”

80
Q

in CRISPR, phage re-infection leads to

A

CRISPR sequences transcribed; crRNAs target phage DNA

81
Q

review slide 7 about CRISPR

A

its got a star on it

82
Q

animal viruses bind ______ on host cell

A

specific receptor proteins

83
Q

what determines the viral tropism

A

specific receptors;
(broad vs narrow tropism; H5N1 bird flu virus)

84
Q

the replication cycle of an animal virus depends on

A

the form of its genome

85
Q

DNA viruses can utilize

A

host replication machinery

86
Q

RNA viruses possess

A

an RNA-dependent RNA-polymerase to transcribe their mRNA

87
Q

Retroviruses use _____ to copy their genomic sequence into DNA

A

reverse transcriptase; for insertion in the host chromosome

88
Q

most animal viruses enter host as _____

A

virions

89
Q

internalized virions undergo

A

uncoating - the genome is released from its capsid

90
Q

uncoating occurs where?

A
  1. at the cell membrane
  2. within endosomes
  3. at the nuclear membrane
91
Q

how to animal viruses form proteins

A

by using ribosomes in the host cytoplasm

92
Q

animal viruses: assembly of new virions occurs where

A

in the cytoplasm or nucleus

93
Q

enveloped viruses: envelope proteins are inserted into

A

the plasma membrane or organelle membrane

94
Q

release of virions from host occurs via

A

lysis or budding

95
Q

DNA viruses properties

A

-genome replication in nucleus
-synthesis of viral proteins outside the nucleus
-entry of viral proteins into nucleus
-viral assembly in nucleus

96
Q

where does genomes replication, synthesis of viral proteins, and viral assembly occur for RNA viruses

A

all occur outside the nucleus

97
Q

papillomavirus life cycle

A

-most common STD; can be oncogenic
-has active reproduction cycle & dormant stage (viral genome integration)
-HPV production tied to development/differentiation of host epithelial cells

98
Q

genome of an RNA virus can serve as a template for

A

translation -> (+)RNA viruses
mRNA synthesis -> (-)RNA viruses
DNA synthesis -> retrovirus

99
Q
A

MicroBiology (16 decks)

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