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Micro and Immuno - Exam 2 > Virus Classification, Structure, and Replicaiton > Flashcards

Virus Classification, Structure, and Replicaiton Flashcards

1
Q

What’s the difference between a Virus and a Bacterium

A

Bacterium can replicate on their own.

Viruses need a host to replicate

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2
Q

What’s the difference between a Virus and a Toxin

A

A virus can replicate given a host.

A toxin is created by a cell.

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3
Q

What are the theories of Virus Origins

A

Cellular Origin

Autopoetic Origin

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4
Q

Autopoetic Origin Theory

A

Proposes that viruses were once autopoetic entities, but became dependent on cells for replication

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5
Q

Cellular Origin Theory

A

Proposes that viruses were once cellular components but over time evolved seperately

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6
Q

Virus Particle Structure can be organized by…

A

Composition
Shape
Size

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7
Q

What is a nucleocapsid?

A

An RNA or DNA in a core that is protected by a protein coat (capsid)

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8
Q

What is a capsid comprised of?

A

Repeating protein subunitys called capsomeres

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9
Q

What are envelopes?

A

Virus-modified cellular membranes that are acquired upon exit from host cells

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10
Q

What happens to enveloped viruses when exposed to lipid solvents in a lab?

A

They are rendered noninfectious

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11
Q

How big is a “small virus”

A

18 nm

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12
Q

How big is a “large virus”

A

300 nm

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13
Q

What is an advantage of a small virus?

A

Small viruses replicate faster

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14
Q

What is an advantage of a large virus?

A

Large viruses carry more immune modulating genes that can allow for more replication and shut down the immune system

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15
Q

What are the different virus genome compositions/classifications

A

DNA - double stranded
DNA - single stranded
RNA - double stranded
RNA - single stranded +, -, or ambisense

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16
Q

What is special about ambisense ssRNA

A

Resembles -ssRNA but it can read +ssRNA or -ssRNA

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17
Q

What are the different structures of virus genome?

A

Linear
Circular
Segmented
Diploid

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18
Q

ssDNA replication

A

Needs a double stranded structure to bind to - uses a hairpin structure. Relies on host cell replication machinery

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19
Q

dsDNA replication

A

Similar to double stranded DNA replication in humans

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20
Q

+ssRNA replication

A

Uses host ribosomes

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21
Q

-ssRNA replication

A

needs RNA dependent RNA polymerase to make + strand, which can serve as a template

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22
Q

What are the steps of virus replication

A 
Attachment
Entry
Transcription
Translation
Replication
Assembly
Release
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23
Q

Virus attachment

A

Virus receptor bind to cellular receptors. They usually don’t mimic normal ligands, and bing somewhere other than the normal binding zone. Still triggers the cascade to cause virus to enter.

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24
Q

Viral receptors

A

Usually don’t mimic cell receptor’s normal ligands.
Typically are spike-like projections on viral particle surface.
May require a co-receptor

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25
What can genetic engineering do to viral attachment?
It can change receptor recognition.
26
What is a major determinate of virus tropism/host range?
Attachment
27
What is a major factor for eradication of a virus?
Host range
28
(T/F) A virus can infect a human and a fungus.
False - a virus range won't cross kingdoms
29
(T/F) A virus can infect all life forms
True
30
What are the pathways of virus entry into a cell?
Receptor mediated endocytosis | Direct penetration of plasma membrane
31
Non-enveloped virus cell entry
Not well understood. | Enters either through pores or membrane disruption
32
Enveloped virus cell entry
Enters through membrane fusion HA proteins aid in attachment of the virus, lowering pH, which causes a conformational change and the membranes fuse (Receptor induced)
33
After entry, what occurs to viruses that undergo nuclear replication?
The genome and remaining protein coat (nucleocapsid) are transported to the nuclear membrane, and the genome gets delivered to the nuclesus
34
After entry, what occurs to viruses that undergo cytoplasmic replication?
The genome is released into the cytoplasm, and the genome gets transported to the intracellular site of replication. Many RNA viruses replicate in membrane associated complexes.
35
What is important about dsRNA viruses upon entry?
It is important that they NEVER release their genome from the entering particle, because this would trigger an immune reponse.
36
+ssRNA virus Transcription
+ssRNA serves as mRNA - and production of new transcripts can occur later using a -ssRNA template
37
-ssRNA and dsRNA transcription
These viruses must bring their own polymerases into the cell
38
DNA virus transcription
These viruses rely on cellular RNA polymerase
39
Virus Translation
All viruses require the cell's ribosomes to produce proteins.
40
Viral proteins production can be regulated at what levels?
Both the transcription and translation levels
41
+ssRNA genome replication
Genome serves as a template for translation. | Polymerase makes -ssRNA copy as a template for the new genome
42
-ssRNA genome replication
Virus particle musct include the viral polymerase Polymerase makes a messenger for translation The genome replicated through a +ssRNA intermediate
43
dsRNA genome replication
Virus particle includes viral polymerase dsRNA induces innate immune response, so the genome stays inside the particle mRNA is synthesized in the particle and is exported to the cytoplasm mRNA serves as the + strand and the - strand is synthesized during assembly
44
ssDNA and dsDNA genome replication
Must gain access to the nucleus, prepare the cell for DNA replication, and ensure the genome ends are copied
45
Virus assembly
Package new genomes into functional particles | Structural proteins are localized to aid in assembly (cellular viral "factories")
46
What are the virus assembly mechanisms?
Adenovirus Reovirus Retrovirus
47
Adenovirus assembly
Empty protein coats import a newly replicated genome
48
Reovirus assembly
RNA is packaged during capsid assembly
49
Retrovirus assembly
Preassembly on a membrane
50
What are the different types of virus release?
Lysis Weak Lysis Budding
51
Lysis release
Best known for bacteriophage | Viral molecule that rupture cellular membrane
52
Weak Lysis release
Depends on membrane breakdown after cell death
53
Budding release
Enveloped viruses use cell membranes as the outer coat of the virus particle
54
What advantages/disadvantages come with targeting virus replication in the nucleus.
It has to go through 2 membranes - the nucleus and the cell
55
How does understanding a virus' replication process help to design antivirals?
Antivirals can be made to target the RNA --> DNA step
56
What advantages/disadvantages come with lytic versus non-lytic infection?
Lytic infection is quicker for progeny to get to other cells, but a higher chance of triggering an immune response
57
Explain the one-step growth curve of viral kinetics
Infects every cell at the same time | All cells die at the end of infection
58
What are the phases of viral kinetics?
Eclipse Exponential growth Plateau
59
Eclipse
Attachment and uptake of virus
60
Exponential growth
Replication and Assembly of virus
61
Plateau
Cell death
62
Initial discovery of viruses
Done by either by disease in a host or contaminant in a cell culture
63
Confirmation of viruses
Purification of a virus | Confirmation of disease (by animals, eggs, or cell culture) - cell culture is prefered
64
What are the Principle of Detection and Quantification Methods
Infectivity Physical Genome Serological
65
Molecular methods are useful for detecting...
Viruses that cannot be cultivated
66
Cytopathic Effect
Cell Rounding Syncytia Formation Inclusion bodies
67
Fluorescent Focus Assay
Infect cells Expose the virus antigen Stain them with labeled antibody Count areas that flouresce
68
Plaque assay
Take a cell monolayer Inoculate it with dilute virus Infected cells die which leave a clear area (plaque)
69
Infectious dose
ID50, IU50, TCID50 Systems: tissue culture, eggs, animals Inoculate these systems with different dilutions of virus Calculate the concentration based on the number infected
70
What are the different Infection Assays?
Cytopathic Effect Fluorescent Focus Assay Plaque assay Infetious dose
71
What are the different Particle Assays?
Electron microscopy | Hemagglutin assay
72
Electron microscopy
Direct image of virus particles | Calibrate with latex bead standard
73
Hemagglutin assay
Used with viruses that bind to RBCs Mix constant number o RBCs with different dilutions of virus If a virus concentration is sufficient, a matrix of RBCs and virus is formed Matrix does not allow RBCs to pellet
74
What are the different genome assays
Polymerase chain reaction (PCR) | Southern (DNA) and Northern (RNA) blots
75
Polymerase chain reaction
Use a DNA primer to a specific virus Amplify the gene Very sensitive
76
Southern and Northern blots
Isolate DNA or RNA Separate by electrophoresis Use labeled DNA probe to detect
77
What are the different serological assays
Virus neutralizaiton Enzyme Link Immunoabsorbant Assay (ELISA) Western (Protein) Blot
78
Virus neutralization
Antibody binding to virus can block infection | Virus concentration determined by amount of antibody needed
79
Enzyme Link Immunoabsorbant Assay
Antibody recognition of virus | Amplification by enzyme linked to antibody
80
Western (Protein) Blot
Separate proteins by electrophoresis | Probe proteins using an antibody

Micro and Immuno - Exam 2 (11 decks)

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