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SP14 Microbiology > Final; Virus Biology > Flashcards

Final; Virus Biology Flashcards

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Biology 101 flashcards
1
Q

What are the two theories of virus origin

A

cellular origin

autopoietic origin

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2
Q

This proposes that viruses were once cellular components but over time they evolved separately

A

cellular origin

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3
Q

This proposes that viruses, once autopoietic entities, became dependent on cells for replication

A

autopoietic origin

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4
Q

What are the attributes that viruses are classified on

A 
particle structure
genome
replication features
serology
stability
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5
Q

What are the components of virus particle structure

A

composition
stucture
size

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6
Q

This is RNA or DNA in a core that is protected by a protein coat

A

nucleocapsid

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7
Q

A virus is defined by what

A

the nucleocapsid structure

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8
Q

What are the different nucleocapsid structures

A

helical
pleomorphic
icosahedral

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9
Q

A nucleocapsid is comprised of what

A

repeating protein subunits called capsomeres

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10
Q

This is a virus-modified cellular membrane acquired upon exit from the host

A

envelopes

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11
Q

This renders enveloped viruses noninfectious

A

exposure to lipid solvents in the laboratory

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12
Q

True or False

Enveloped viruses may have nucleocapsids with different structures

A

True

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13
Q

What are the lengths of the smallest and largest virus particle

A

smallest; 18nm

largest; 300nm

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14
Q

What are the different combinations of the viral genome

A

double or single stranded

DNA or RNA

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15
Q

What different types of single stranded RNA can you have

A

plus sense ssRNA
minus sense ssRNA
ambisense

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16
Q

Which type of ssRNA can be used directly for translation

A

plus sense

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17
Q

What must happen to minus sense ssRNA before translation

A

a positive (plus sense) copy must be made

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18
Q

What are the different structures (gene arrangement) of the viral genome

A

linear
circular
segmented
diploid

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19
Q

How can viruses not follow the central dogma

A

They are able to revert from RNA to DNA via reverse transcriptase

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20
Q

What do most DNA viruses need that RNA viruses do not

A

access to the nucleus

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21
Q

What do RNA viruses need that DNA viruses do not

A

the ability to make positive/negative strands

reverse transcriptase

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22
Q

What is the process of viral replication

A 
attachment
entry
transcription
translation
replication
assembly
release
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23
Q

How does a virus attach to a cell

A

via receptors

the cell does not have viral receptors, the virus binds to already functional receptors on the cell

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24
Q

What type of cell receptors do viruses bind to

A

signaling
cell adhesion
transport

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25
Q

How to viruses attach to the cell receptors

A

do not mimic cell receptor ligands
typically spike like projections
may require co-receptor

26
Q

This is a major determinant of virus tropism (host range)

A

attachment

27
Q

True or False

Viruses are only specific to humans

A

False; viruses are known to infect essentially all forms of life

28
Q

This is a major factor in eradication

A

host range

29
Q

What are the pathways of viral entry

A

receptor mediated endocytosis

direct penetration of plasma membrane

30
Q

How can non-enveloped viruses entry the cell

A

its not well understood

perhaps through pores or membrane disruption

31
Q

In what ways can enveloped viruses enter the cell

A

membrane fusion

receptor conformational change (pH; receptor induced)

32
Q

How does nuclear replication occur

A

the genome and remaining protein coat are transported to the nucleus to deliver the genome

33
Q

How does cytoplasmic replication occur

A

genome is released into cytoplasm to site of replication

many RNA viruses replicate in MACs

34
Q

dsRNA viruses never release what

A

their genomic material from the entering particle

35
Q

DNA viruses rely on what for transcription

A

cellular RNA polymerases

36
Q

The genome of what can serve was mRNA

A

+ssRNA

37
Q

These RNA viruses must bring their own polymerases into the cell

A

-ssRNA

dsRNA

38
Q

All viruses need what to produce proteins

A

the cells ribosomes

39
Q

Non-structural proteins are only seen where

A

inside the infected cell

40
Q

The order of genomic replication of viruses depends on what

A

virus genome

41
Q

This induces innate immune response so the genome stays inside the particle

A

dsRNA

42
Q

The dsRNA mRNA is synthesized where

A

inside the particle and is then transported to the cytoplasm

43
Q

Why are poxviruses an exception to the DNA viruses needing access to the nucleus

A

virion contains the necessary RNA polymerase and the genome encodes the DNA polymerase for replication

44
Q

What is the function of viral assembly

A

to package new genomes into functional particles

45
Q

What aids in assembly

A

localized structural proteins; cellular viral “factories”

the genome contains packaging signals

46
Q

How does an adenovirus undergo assembly

A

empty protein coat imports genome

47
Q

How does a reovirus undergo assembly

A

RNA packaged during capsid assembly

48
Q

How does a retrovirus undergo assembly

A

reassembly on a membrane

49
Q

What are the different types of viral releases

A

lysis
weak lysis (impair membrane repair)
budding (enveloped only)

50
Q

What are the kinetic phases of viral replication

A

eclipse; attachment and uptake
exponential growth; replication and assembly
plateau; cell death

51
Q

True or False
There is a variety of the length of time it takes for a virus to go from the start on an infection to the beginning of a plateau

A

True;
bacteriophage; 30 mins
vaccina; 24 hours

52
Q

What is the productivity of a virus

A

measure amplification
vesicular stomatitis virus (VSV) 1:1000
vaccina 1:100

53
Q

What methods are used to initially discover a virus

A

disease in host

contaminant in cell culture

54
Q

What methods are used to confirm a virus

A

purification

confirmation of disease; animals, eggs, or cell culture (preferred)

55
Q

What are the principle of detection and quantification methods

A

infectivity
physical
genome
serological

56
Q

These methods are useful for viruses that cannot be cultivated

A

molecular methods

57
Q

What are four types of infection assays

A

cytopathic effect (CPE)
fluorescent focus assay
plaque assay
Infectious dose

58
Q

What are two types of particle assays

A

electron microscopy

hemagglutinin assau

59
Q

What are two types of genome assays

A

PCR

southern (DNA) and northern (RNA) blots

60
Q

What are three types of serological assays

A

virus neutralization
enzyme linked immunosorbant assay (ELISA)
western (protein) blot

61
Q

True or False

Different methods of viral detection and quantification give different answers

A

True

62
Q

What is the average diameter of a human virus

A

30-300nm

SP14 Microbiology (31 decks)

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