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Microbiology > test four lec 19 > Flashcards

test four lec 19 Flashcards

1
Q

what are acute viruses

A

kill their host

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2
Q

what happens in lysogenic cycle

A

bacteriophage is quiescent
integrates into cell chromosome as prophage
can reactivate to become lytic
transduction

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3
Q

what are prions

A

proteins that infect animals

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4
Q

what is a viral capsid composed of

A

repeated protein subunits

maximizes capacity while minimizing the required number of genes

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5
Q

how does slow release work

A

filamentous phages can extrude individual progeny through cell envelope
host cells grow slowly but dont die
use SS DNA to create DS DNA and reproduce

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6
Q

what makes ocean viruses different

A

most numerous and genetically diverse forms of life

control algae bloom

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7
Q

viral ecologists believe what of viruses

A

living entities

predator or parasite

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8
Q

how are animal viruses cultured

A

within whole animals by serial inoculation
ensures virus maintains its original virulence
can also grow in human cell tissue culture

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9
Q

what is the function of a capsid

A

packages the viral genome and delivers it into the host cell

they vary based on virus

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10
Q

what are the seven fundamental groups of viral species by baltimore virus classification

A 
DS DNA
SS DNA
DS RNA
\+ SS RNA
- SS RNA
RNA retrovirus
DNA pararetrovirus
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11
Q

what dictates wether lytic or lysogenic

A

environmental cues

threaten host cell survival

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12
Q

what type of defenses have bacteria created against bacteriophage infection

A 
genetic resistance
(alter receptor proteins)
restriction endonucleases
CRISPR
(integration of phage DNA sequences)
bacterial immune system
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13
Q

how can you measure relatedness of different viruses of a common ancestor

A

comparing their genome sequence

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14
Q

what is a virus

A

a non cellular particle that must infect a host cell, where it reproduces

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15
Q

what is used to reveal common descent of viruses with shared infected hosts

A

statistical analysis

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16
Q

what are viroids

A

RNA molecules that infect plants

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17
Q

what allows viruses to attach to host cells

A

cell surface receptors

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18
Q

what is the baltimore virus classification

A

primary distinction among classes of viruses is genome composition and the route used to express messenger RNA

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19
Q

how are viral genomes classified

A 
baltimore method
viral proteins
capsid
envelope proteins
polymerase
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20
Q

how does lysis work

A

make enzyme that breaks down cell wall

host cell bursts to release progeny phage

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21
Q

what type of curve do batch cultures of viruses create

A

step curve

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22
Q

what is the envelope like in an icosahedral virus

A

contains glycoprotein spikes

teguments are present inbetween the envelope and capsid

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23
Q

what is a virion

A

a virus particle

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24
Q

do viruses play a significant role in carbon balance

A

yes

25
Q

when do you use proteomic classification

A

useful of viruses because their small genomes encode few proteins

26
Q

how do viruses fill important niches in all ecosystems

A

limiting host population density

selecting for host diveristy

27
Q

what type of genome do large viruses have

A

more than 100 genes

28
Q

what are bacterial cell receptors used for

A

sugar uptake (maltose)

29
Q

how does a new virus emerge to sicken humans

A

humans eat wildlife
(SARS)
as variants of endemic milder pathogen
(H7N9)

30
Q

what environment can you find viruses

A

all types

31
Q

what are the characteristics of a filamentous virus

A 
capsid consists of a long tube of protein
genome coiled inside
vary in length (genome size)
include bacteriophage and animal viruses
helical symmetry (tube around genome)
usually contain ss DNA and RNA
32
Q

what type of organism does viruses infect

A

all types

33
Q

what are cell surface receptors

A

proteins that are specific to the host species and which bind to a specific viral component

34
Q

what are the two types of life cycles of bacteriophages

A

lytic

lysogenic

35
Q

how do viruses infect hosts

A

mimicking by spreading “computer viruses” whose info “infects” computer memory

36
Q

the pox virus has what type of capsid

A

genome surrounded by several layers
(core envelope with outermembrane)
contain large number of accessory proteins

37
Q

how do you culture viruses

A

requires growth in host cell

bacteriophages cultured either in batch culture or as isolate plaques on a bacterial lawn

38
Q

how do viroids replicates

A

they use the host RNA polymerase

39
Q

what are the characteristics of icosahedral viruses

A

polyhedral
20 identical triangular faces
rational symmetry
capsid is enclosed in an envelope

40
Q

acute vs persistant viruses

A

acute outnumbers in natural ecosystems

41
Q

what are orthologs

A

genes of common ancestry in two genomes that share the same function

42
Q

what is the criteria that is used by the ICTV over virus taxonomy

A 
genomes composition
capsid symmetry
envelope
size of the virion
host range
43
Q

what are the two types of symmetrical viruses

A

icosahedral and filamentous

44
Q

what are the two types of capsids

A

symmetrical and asymmetrical

45
Q

what happens in the lytic cycle

A

bacteriophage quickly replicates killing host cell

cause cell to burst, releasing new phages

46
Q

what type of genome do small viruses have

A

small

encoding under 10 genes, which may overlap in sequence

47
Q

what does a virion consist of

A

a single nucleic acid (DNA or RNA) contained within a protective protein capsid

48
Q

what are persistant viruses

A

along for the ride

may evolve traits that confer positive benefits in a virus-host mutualsim

49
Q

what is needed for host infection

A

host recognition and attachment
genome entry
assembly of virions
exit and transmission

50
Q

what is transduction

A

take host genome and pass it on to other cells

51
Q

how do most viruses interact with hosts

A

positively

express host genes and by protecting hosts from other organisms

52
Q

what characteristic does T4 bacteriophages have with asymmetrical

A

have icosahedral head and helical neck

53
Q

what are proteoms

A

proteins encoded by genomes

54
Q

what is injected from phages into host cell

A

only genome through cell envelope
phage capsid remain outside
“ghost”

55
Q

characteristic of asymmetrical viruses

A

complex multipart structures

56
Q

what is required for viruses to replicate

A

require host cell

57
Q

do viroids have protein capsids

A

no

58
Q

what makes prions different

A

they have NO nucleic acid component

have abnormal structure that alters the conformation of other normal proteins

59
Q

what type of genome comparison is used when finding common ancestor

A

orthologs

Microbiology (16 decks)

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