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MicroBiology > Ch 6 > Flashcards

Ch 6 Flashcards

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
Tailed viruses add a _________ to the icosahedral head
genome delivery device
26
T4 bacteriophages have what kind of fibers
helical "neck" & tail fibers
27
asymmetrical viruses lack
capsid symmetry
28
symmetry of influenza viruses
Asymmetrical
29
Coronavirus properties
-nucleocapsid proteins -enveloped viruses
30
Genome of Zika Virus
-non-segmented, single-stranded, (+) RNA genome -10,794 bp long
31
influenza virus genome
-segmented, single-stranded (-) RNA genome; 8 segments -11 proteins encoded; 13,500 bp total
32
viroids definition
RNA molecules without a capsid surrounding the RNA
33
what do viroids infect
plants
34
Are viroids viruses?
NO
35
sizes of small and large viruses
small: less than 10 genes large: more than 100 genes
36
properties of viroids
-replicated by host RNA polymerase -RNA does NOT encode for proteins; 300-400 NT long -some have catalytic ability
37
effect of viroids
alter gene expression in affected plants
38
Prions definition
proteins that infect animals; NO nucleic acid component -misfolded form of a normal brain cell protein
39
prions convert
a normal protein into the prion version, creating a chain reaction and producing a harmful aggregate in the cell
40
prions can cause
-degenerative brain diseases; creutzfield-jacob disease in humans; scrapie
41
how are prions transmitted
in food prepared from infected animals; highly resistant to physical and chemical agents
42
prion step-by-step invasion
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
viral ecology
important roles in ecosystems; limits host population densities; recycle nutrients; increase host diversity; gene transfer
44
viral shunt
viral infection of hosts convert them to detritus, rich in organic & inorganic molecules
45
check if we need to know mimivirus and pithovirus
unclear
46
international committee on taxonomy of viruses based on
-genome -capsid symmetry -envelope -host range -virion size
47
baltimore classification
-genome (RNA or DNA) & route used to express mRNA
48
+RNA = mRNA =
"sense" RNA
49
Group I viruses
dsDNA -> +mRNA
50
Group II viruses
(+)ssDNA -> dsDNA -> +mRNA
51
Group III viruses
dsRNA -> +mRNA
52
Group IV viruses
(+)ssRNA -> (-)RNA -> +mRNA
53
Group V viruses
(-)ssRNA -> +mRNA
54
Group VI retroviruses
(+)RNA -> (-)DNA -> dsDNA -> +mRNA
55
Groups 3, 4, 5 use
RNA dependent RNA polymerase (RDRP)
56
reverse transcriptase is used in which group
Group VI retroviruses
57
do we need to know all the virus examples in baltimore classification
thats like 22 viruses
58
all viral life cycles comprise these events
1. host recognition & attachment 2. genome entry 3. synthesis & virion assembly 4. exit & transmission
59
host recognition & attachment occurs via ______ to host cell surface proteins or glycoproteins
-recognition/binding of viral capsid proteins -envelope proteins -glycoproteins
60
in genome entry, the entire capsid + genome ____
enters host cell (or only the genome may enter)
61
synthesis and virion assembly involves
-genome replication -proteins synthesis -assembly of virions
62
what happens in exit & transmission
release from host cell -> progeny infect more host cells
63
the lytic cycle and lysogenic cycle are
bacteriophage life cycles
64
lytic cycle
-T even phages -phage quickly replicates
65
lysogenic cycle phage type
-lambda phage; temperate phages
66
which bacteriophage cycle kills the host quicker
lytic cycle - kills host immediately; lysogenic cycle does not necessarily kill host right away
67
in lysogenic cycle, the phage integrates into the cell chromosome as a _______
prophage (site-specific recombination)
68
lysogenic cycle phages can ______ to become ______
reactivate; lytic
69
what dictates when lysogeny converts to the lytic cycle
environmental cues / the health of the cell
70
"virulent" phages only carry out which cycle
lytic cycle (T4)
71
temperate phages cycle between
lysis and lysogeny (e.g. lambda phage
72
slow release bacteriophages ->
M13 filamentous phage (ssDNA)
73
M13 phage particles reproduce and ____
exit without harming the host cell which grow slowly but don't die
74
types of bacterial host defenses
-genetic resistance -restriction endonucleases
75
how does genetic resistance work as a host cell defense
receptor proteins are altered
76
how does restriction endonuclease work as a host cell defense
by cleaving viral DNA sequences lacking methylation
77
bacterial DNA is methylated on the
cytosine nucleotides
78
CRISPR stands for
Clustered Regularly Interspaced Short Palindromic Repeats
79
in CRISPR, host cleaves phage DNA and inserts
fragment into chromosome as a "spacer"
80
in CRISPR, phage re-infection leads to
CRISPR sequences transcribed; crRNAs target phage DNA
81
review slide 7 about CRISPR
its got a star on it
82
animal viruses bind ______ on host cell
specific receptor proteins
83
what determines the viral tropism
specific receptors; (broad vs narrow tropism; H5N1 bird flu virus)
84
the replication cycle of an animal virus depends on
the form of its genome
85
DNA viruses can utilize
host replication machinery
86
RNA viruses possess
an RNA-dependent RNA-polymerase to transcribe their mRNA
87
Retroviruses use _____ to copy their genomic sequence into DNA
reverse transcriptase; for insertion in the host chromosome
88
most animal viruses enter host as _____
virions
89
internalized virions undergo
uncoating - the genome is released from its capsid
90
uncoating occurs where?
1. at the cell membrane 2. within endosomes 3. at the nuclear membrane
91
how to animal viruses form proteins
by using ribosomes in the host cytoplasm
92
animal viruses: assembly of new virions occurs where
in the cytoplasm or nucleus
93
enveloped viruses: envelope proteins are inserted into
the plasma membrane or organelle membrane
94
release of virions from host occurs via
lysis or budding
95
DNA viruses properties
-genome replication in nucleus -synthesis of viral proteins outside the nucleus -entry of viral proteins into nucleus -viral assembly in nucleus
96
where does genomes replication, synthesis of viral proteins, and viral assembly occur for RNA viruses
all occur outside the nucleus
97
papillomavirus life cycle
-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
genome of an RNA virus can serve as a template for
translation -> (+)RNA viruses mRNA synthesis -> (-)RNA viruses DNA synthesis -> retrovirus
99

MicroBiology (16 decks)

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