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microbiology > virology intro > Flashcards

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
Q

Adsorption of Virions

A

• viral surface proteins and/or enzymes mediate attachment to specific host receptors

26
Q

Penetration and Uncoating

A

• three mechanisms
– injection of nucleic acid
– fusion of envelope with host membrane
– endocytosis

27
Q

injection of NA

A
28
Q

envelope fusion mechanism

A
29
Q

endocytosis penetration by virus mechanism

A
30
Q

single-stranded +RNA viruses

pro synthesis and genome replication

A
31
Q

single-stranded -RNA viruses

pro synthesis and genome replication

A
32
Q

double-stranded RNA viruses

pro syn and DNA replication

A
33
Q

retroviruses

pro syn and genome replication

A
34
Q

hepadnaviruses

pro syn and genome replication

A
35
Q

single-stranded DNA viruses

pro syn and genome replication

A
36
Q

double-stranded DNA viruses

pro syn and genome replication

A
37
Q

double-stranded DNA viruses

pro syn and genome replication

A
38
Q

Assembly of Virus Capsids
capsid pro encoded by?
naked vs enveloped viruses
site?

A

• 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
Q

Virion Release of naked viruses

A

usually by lysis of host cell

40
Q

virion release of enveloped viruses

A

– 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
Q

Virus replication events during a single infectious cycle

titer level during the events?

A

release occurs during assembly as well

42
Q

Typical transcription pattern for a DNA virus

A

early genes for replication/pro syn

late genes for exit

43
Q

possible Pathobiology of viral diseases

A
44
Q

Viral encounter and entry

A 
respiratory
GI/ Oral 
lesion 
blood/body fluid 
insect bites
45
Q

bacteriophages part of?

A

human virome, bind various receptors

46
Q

possible cycles of bacteriophage reproduction

A

lysis/ lysogeny

slow release

47
Q

lytic cycle of bacteriophage reproduction

A 
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
Q

lysogeny cycle of bacteriophages

A

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
Q

lysogeny to lytic cycle transition

A

stress may induce the excision of phage DNA

DNA can recombine to form circular form and enter lytic cycle

50
Q

phage c1 provides gene for

A

botinulum toxin

51
Q

beta phage provides gene for

A

diptheria toxin

52
Q

epsilon 34 provides gene for

A

LPS synthesis

53
Q

HERV-W retrovirus provides the gene for?

A

placental fusion

54
Q

HERV-E retrovirus provides the gene for?

A

liver function

55
Q

slow release of bacteriophage

A

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
Q

bacterial defenses against phages

A

Genetic resistance – mutations in bacterial genes (e.g. receptor)
Restriction endonucleases – enzymes that cut invading DNA
CRISPR – a bacterial immune system

57
Q

CRISPR

A

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
Q

phage assistance with bacterial infections and immune reactions
possible treatments?

A

being explored as a possible antibiotic replacement

microbiology (42 decks)

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