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BMSC 210 > Chapter 8 > Flashcards

Chapter 8 Flashcards

1
Q

archaea viruses

A
  • great diversity

- major role in oceanic microbiomes

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2
Q

how do archaea viruses differ from eukaryotic and bacterial viruses

A

in genome, morphology, architecture, and protein encoding

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3
Q

virus

A

genetic element that cannot replicate independently of a living host

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4
Q

virology

A

study of viruses

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5
Q

virus particle/virion

A
  • extracellular form of a virus

- exists outside the host and facilitates transmission from host to another

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6
Q

virion make up

A

nucleic acid genome surrounded by protein coat and, in some cases, other layers of material (phospholipid membrane with viral glycoproteins)

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7
Q

characteristics of viruses

A
  • infectious, acellular, pathogens
  • obligate intracellular parasites with host and cell-type specificity
  • DNA or RNA genome; never both
  • lack genes for reproduction requiring exploitation of host-cell genomes to reproduce
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8
Q

viral genomes are sometimes circular, but most….

A

linear

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9
Q

RNA viruses that contain ___ can be directly read by ribosomes to synthesize viral proteins

A

+ssRNA

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10
Q

viruses containing ____ must use the _____ template for the synthesis of _____ before viral proteins can be made

A

-ssRNA, -ssRNA , +ssRNA

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11
Q

+ssRNA

A

positive single stranded RNA

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12
Q

-ssRNA

A

negative single strand RNA

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13
Q

viruses can be classified on the basis of…

A

the host they infect

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14
Q

new classification schemes call for classification of viruses base on…

A

nucleic acid similarities

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15
Q

viruses size

A

usually smaller than prokaryotic cells at 0.02 - 0.3 um

-most viral genomes smaller than those cells

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16
Q

caspid

A

the protein shell that surrounds the genome of a virus particle

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17
Q

caspid composition

A

of protein molecules arranged in precise and highly repetitive pattern around the nucleic acid

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18
Q

capsomere

A

subunit of capsid

-smallest morphological unit visible with an electron microscope

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19
Q

nucleocapsid

A

complete complex of nucleic acid and protein packaged in virion

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20
Q

enveloped virus

A

virus that contains additional layers around the nucleocapsid (lipid bilayer with embedded proteins)
-envelop makes initial contact with host

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21
Q

arrangement of nucleic acid and protein coat in a simple virus

A

RNA assumes a helical configuration surrounded by the protein capsid
-centre is hollow

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22
Q

in ro-shaped viruses, length is determined by ___ and width is determined by ___

A

length: length of nucleic acid
width: size and packaging of protein subunits

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23
Q

icosahedral symmetry

A

spherical viruses

-most efficient arrangement of subunits in a closed shell

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24
Q

influenza virus envelop

A

contains spikes of hemagglutinin and neuraminidase forming a halo of predictions around negatively stained virus particles

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25
Q

ebola virion composition

A
  • helical
  • spikes of envelop
  • lipid envelope
  • membrane associated proteins
  • nucleocapsid proteins
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26
Q

if a virion has a _____, they might infect humans

A

lipid envelope

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27
Q

complex viruses composition

A

several parts, each with separate shapes and symmetries

-icosahedral head and helical tail

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28
Q

most phages contain ____ genome

A

dsDNA (double stranded)

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29
Q

enzymes in virions critical to infection

A
  • lysozyme-like
  • nucleic acid polymerase
  • neuraminidases
30
Q

lysozyme- like enzymes

A
  • make hole in cell wall

- lysis bacterial cell in later stages of infection to release new virions

31
Q

nucleic acid polymerase

A

RNA virus-RNA dependent RNA polymerase, also called RNA replicase
-reverse transcriptase (retroviruses)

32
Q

neuraminidases

A

(influenza virus)

  • enzymes that cleave glycosidic bonds
  • allows liberation of viruses from cell
33
Q

viruses replicate only in…

A

certain types oc cells or in whole organisms

34
Q

what kind of viruses are the easiest to grow?

A

bacterial viruses

35
Q

titer

A

number of infectious units per volume fluid

36
Q

plaque assay

A

analogous to the bacterial colony; one way to measure virus infectivity

37
Q

plaques

A

clear zones that develop on lawns of host cells

  • lawns = bacterial or tissue cultures
  • each plague results from infection by a single virus particle
38
Q

efficiency of plating

A

used in qualitative virology

39
Q

number of plaque-forming units is almost always lower than direct counts due to…

A
  1. inactive virions

2. conditions not appropriate of infectivity

40
Q

phases of viral replication

A
  1. attachment (adsorption)
  2. entry (penetration)
  3. synthesis
  4. assembly
  5. release
41
Q

latent period

A

eclipse + maturation

-early enzyme, nucleic acid, protein coats

42
Q

burst size

A

number of virions released

43
Q

lambda bacteriophages of e.coli

A
  • head & tail
  • dsDNA
  • circular
44
Q

MS2 bacteriophages of e.coli

A
  • icosahedral
  • ssRNA
  • linear
45
Q

T7 and T3 bacteriophages of e.coli

A
  • head &tail
  • dsDNA
  • linear
46
Q

attachment of virion to host cell is…

A

highly specific

47
Q

permissive cells

A

host cell that allows the complete replication of cycle of a virus

48
Q

T4 attached to cells via…

A

tail fibres that interact with polysaccharides on the E.coli cell envelop

49
Q

attachment of virus to its host cell results in…

A

changes on both virus and cell surface that facilitate penetration

50
Q

mechanisms to diminish viral infections in eukaryotes and prokaryotes…

A
  • immune defence mechanisms, RNA interference
  • restriction modification systems
  • viruses can evade bacterial restriction systems
51
Q

restriction modification systems

A
  • only effective against dsDNA viruses

- mod. of host’s own DNA at RE recognition sites prevents cleavage of its DNA

52
Q

mechanisms to diminish viral infections in bacteria

A

chemical modification of viral DNA (lycosylation or methylation)
-production of proteins that inhibit host cell RE system

53
Q

T4 genome can be divided into what 3 parts?

A

early, middle and late genes

54
Q

early and middle proteins

A

enzymes needed for DNA replication and transcription

55
Q

late proteins

A

head and tail proteins and enzymes required to liberate mature phage particles

56
Q

packaging of T4 genome

A
  1. procurer of bacteriophage head is assembled
  2. packaging motor is assembled
  3. dsDNA is pumped into head under pressure using ATP
  4. after head is filled with DNA, T4 tail, tail fibres, and other components are added
57
Q

virulent mode

A

burst size is 100 virions

58
Q

temperate mode

A

can undergo a stable genetic relationship within the host

- can also kill through lytic cycle

59
Q

lysogeny

A

state where most virus genes are not expressed and virus genome (prophage) is replicated in synchrony with host chromosomes

60
Q

prophage

A

virus genome

61
Q

lysogen

A

a bacterium containing a prophage

62
Q

animal virus infection stages

A
  1. entire virion enters cell
  2. eukaryotic cells contain a nucleus which is the site of replication for most animal viruses
  3. animal viruses contain all know moded of viral replication
  4. many more kinds of enveloped animal viruses than bacterial viruses
63
Q

influenza

A

ssRNA -

64
Q

acquired immunodeficiency syndrome (AIDs)

A

ssRNA/dsDNA (retrivirus +)

65
Q

ebola hemorrhagic fever

A

ssRNA -

66
Q

sever acute respiratory syndrome (SARS)

A

ssRNA +

67
Q

persistent infections

A

slow release of virus without causing cell death

68
Q

latent infections

A

virus present but not replicating

69
Q

transformation

A

tumour cell division

70
Q

cell fusion

A

to host cell surface

71
Q

replication of retrovirus

A
  1. entry/un-coating retrovirus
  2. reverse transcriptase activity
  3. viral DNA enter nucleus and integrated into the host genome
  4. transcription by host RNA poly. forms viral mRNA and genome copies
  5. translation of mRNA for viral proteins

BMSC 210 (4 decks)

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