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virology intro Flashcards

1
Q

Viruses versus cellular organisms

A
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2
Q

theories of viral origin

A

reductive
intracellular
independent

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3
Q

reductive theory of viral origin

A

intracellualr parasite infects cell and reduces the amt of genetic material it possesses to a form a DNA virus

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4
Q

intracellular origin of viruses

A

functional parts of cell that acquired the ability to reproduce themselves uncontrolled by the cell, formed retroviruses

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5
Q

independent origin of viruses

A

viroid nucleic acids evolved outside the cells in the “RNA world” and acquired ability to infect cells

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6
Q

size of viruses

A

smaller than bac

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7
Q

largest virus

A

pandoravirus

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8
Q

multicomponent viruses

A

Multicomponent viruses genomes are segmented and the segments are distributed into separate viral particles

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9
Q

infection by multicomponent viruses

A

multiple distinct particles are required for infection

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10
Q

Cultivation of viruses requires:
examples?
what might you see?

A 
inoculation of living host cell
• suitable animals
• embryonated eggs
• tissue (cell) cultures
– monolayers of animal cells

plaques= localized area of cellular destruction and lysis

• cytopathic effects (CPEs)
– microscopic or macroscopic degenerative changes or abnormalities in host cells and tissues

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11
Q

basic viral structure

A

delivery system and a payload
Delivery system = structural components that enable the virus to survive and bind host cells
Payload = viral genome and enzymes required for initial steps of replication

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12
Q

naked capsid and envolped viruses strucutres

A
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13
Q

Icosahedral symmetry

A
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14
Q

famous virus with Icosahedral symmetry

A

HSV-1 (herpes)

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15
Q

tails of viruses

A

may be present to attach to host cells

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16
Q

helical symmetry

A

nucleic acid coated with proteins in a helical conformation

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17
Q

ebola has what symmetry

A

helical symmetry

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18
Q

Enveloped vs. nonenveloped viruses structures (with the different symmetry too)

A
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19
Q

Asymmetrical viruses

A

genome with no symmetry, usually surrounded with capsid or membrane

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20
Q

vaccina pox virus symmetry

A

asym

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21
Q

Main groups of human RNA viruses

A
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22
Q

Main groups of human DNA viruses

A
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23
Q

Viruses are classified using a combination of properties:

A
  • Type and structure of nucleic acid used for viral genome
  • Presence or absence of envelope
  • Type of capsid symmetry
  • Replication strategy
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24
Q

Virus Replication steps

A 
–adsorption
–penetration and uncoating
–synthesis of viral proteins and nucleic acids
–assembly of virions
–release
25
Adsorption of Virions
• viral surface proteins and/or enzymes mediate attachment to specific host receptors
26
Penetration and Uncoating
• three mechanisms – injection of nucleic acid – fusion of envelope with host membrane – endocytosis
27
injection of NA
28
envelope fusion mechanism
29
endocytosis penetration by virus mechanism
30
single-stranded +RNA viruses | pro synthesis and genome replication
31
single-stranded -RNA viruses | pro synthesis and genome replication
32
double-stranded RNA viruses | pro syn and DNA replication
33
retroviruses | pro syn and genome replication
34
hepadnaviruses | pro syn and genome replication
35
single-stranded DNA viruses | pro syn and genome replication
36
double-stranded DNA viruses | pro syn and genome replication
37
double-stranded DNA viruses | pro syn and genome replication
38
Assembly of Virus Capsids capsid pro encoded by? naked vs enveloped viruses site?
• capsid proteins – encoded by late genes • assembly of naked viruses – empty procapsids formed then nucleic acid inserted • assembly of enveloped viruses – in most cases, similar to assembly of naked viruses • site of morphogenesis varies
39
Virion Release of naked viruses
usually by lysis of host cell
40
virion release of enveloped viruses
– formation of envelope and release usually occur concurrently • virus-encoded proteins incorporated into host membrane • nucleocapsid buds outward and is surrounded by modified host membrane
41
Virus replication events during a single infectious cycle | titer level during the events?
release occurs during assembly as well
42
Typical transcription pattern for a DNA virus
early genes for replication/pro syn | late genes for exit
43
possible Pathobiology of viral diseases
44
Viral encounter and entry
``` respiratory GI/ Oral lesion blood/body fluid insect bites ```
45
bacteriophages part of?
human virome, bind various receptors
46
possible cycles of bacteriophage reproduction
lysis/ lysogeny | slow release
47
lytic cycle of bacteriophage reproduction
``` phage inserts DNA to host cell, can cyclize into circular form cell synthesizes capsid proteins replication of phage DNA DNA packaged into capsids cell is lysed an progeny are released ```
48
lysogeny cycle of bacteriophages
occurs when condition are favorable, cell is not lysed | phage DNA inserted into host genome and replicated when cell divides= produces population with phage genome present
49
lysogeny to lytic cycle transition
stress may induce the excision of phage DNA | DNA can recombine to form circular form and enter lytic cycle
50
phage c1 provides gene for
botinulum toxin
51
beta phage provides gene for
diptheria toxin
52
epsilon 34 provides gene for
LPS synthesis
53
HERV-W retrovirus provides the gene for?
placental fusion
54
HERV-E retrovirus provides the gene for?
liver function
55
slow release of bacteriophage
will maintain cell, cell divides more slowly though due to resources being used to make phages DNA inserted, forms a circle DNA replicated phages assembled and exit without lysis cell reproduces slowly during this
56
bacterial defenses against phages
Genetic resistance – mutations in bacterial genes (e.g. receptor) Restriction endonucleases – enzymes that cut invading DNA CRISPR – a bacterial immune system
57
CRISPR
viral DNA injected into bacteria is cleaved and a spacer is formed in the genome later infection causes expression of spacers into crRNAs that associated with CAS enzyme allows CAS to target viral DNA= destroy it
58
phage assistance with bacterial infections and immune reactions possible treatments?
being explored as a possible antibiotic replacement

microbiology (42 decks)

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