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MCB 4403 > Lecture 8 > Flashcards

Lecture 8 Flashcards

1
Q

Viruses contain a ___ or ___ genome that codes for functions required for _________

A

DNA or RNA, self perpetuation

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2
Q

The viral genome is enclosed in a protective coat called

A

the capsid

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3
Q

What is the function of the capsid? (2)

A
  • Protects the genome
  • Ensures the attachment into susceptible cells
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4
Q

a virus particle is called a

A

virion

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5
Q

What are the two portions of the life cycle for viruses and what do they do?

A
  • extracellular phase: virus particles (virions) aren’t metabolically active
  • intracellular phase: virus genome expression and production of new virus progeny occurs
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6
Q

viruses are classified as what kind of pathogens?

A

obligate intracellular pathogens

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7
Q

At the minimum, all viruses have

A
  • A DNA or RNA genome
  • A capsid, a protein shell
  • A polymerase
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8
Q

What else can viruses have on top of the minimum?

A
  • Envelope, a lipid membrane
  • Spiked proteins
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9
Q

Classification of Viruses: Group I

A

dsDNA

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10
Q

Baltimore Classification of Viruses: Group II

A

ssDNA

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11
Q

Baltimore Classification of Viruses: Group III

A

dsRNA

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12
Q

Baltimore Classification of Viruses: Group IV

A

(+) ssRNA

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13
Q

Baltimore Classification of Viruses: Group V

A

(-) ssRNA

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14
Q

Baltimore Classification of Viruses: Group VI

A

RNA retroviruses (+)

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15
Q

Baltimore Classification of Viruses: Group VII

A

DNA pararetroviruses

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16
Q

where can viral genomes be found in our own genomes? (2)

A
  • placenta
  • syncytin
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17
Q

viruses infect what forms of living cells?

A

ALL OF THEM

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18
Q

Peyton Rous discovered what?

A

some viruses can cause cancer! (based on the picture)

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19
Q

what was the conclusion of the Hershy-Chase experiment?

A

DNA (not protein) is the genetic material

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20
Q

Temin Baltimore discovered what kind of virus?

A

retrovirus

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21
Q

what makes retroviruses different?

A

they use reverse transcriptase to turn viral RNA into DNA to be used in host cells to create more DNA

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22
Q

non-envelope viruses include…

A

adenoviruses

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23
Q

What do the nucleocapsid of non-envelope viruses contain?

A

nucleocapsid contains attachment proteins

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24
Q

envelope viruses contain

A

attachment proteins

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25
Q

viral envelopes are made of _____ and are sensitive to _____ and _____

A

lipids; detergent, bleach

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26
Q

T/F: non-envelope viruses are sensitive to detergent

A

FALSE- they are not sensitive to detergen

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27
Q

capsids can have what kind of symmetry? (3)

A
  • helical
  • icosahedral
  • complex
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28
Q

capsomere

A

building blocks of capsids

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29
Q

tube length reflects what about the viral genome?

A

size of the genome

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30
Q

complex capsids can be shaped like what..?

A

a mixture of icosahedral and filamentous shapes

31
Q

T/F: viral genomes can be both RNA and DNA at the same time

A

FALSE- they can be either RNA or DNA but not both

32
Q

visual classifications of the viral genome (6)

A
  • single stranded
  • double stranded
  • circular
  • sense (+) or antisense (-)
  • segmented
  • double stranded segmented
33
Q

viroids only contain..

A

RNA, no protein

34
Q

what are viroids capable of infecting?

A

plants

35
Q

prions contain…

A

only protein, no nucleic acids

36
Q

T/F: all viruses have envelopes

A

FALSE

37
Q

T/F: all viruses have to produce mRNAs during their life cycles

A

TRUE

38
Q

Viral genomes can be which of the following configurations?
- DNA
- dsRNA
- ss(+) RNA
- ss(-) RNA
- All of the above

A

all of the above

39
Q

what must viruses be grown in to study them?

A

in living cells

40
Q

to study animal and plant viruses, they may be grown in what?

A

cell cultures

41
Q

cytopathic effect

A

refers to structural changes in host cells that are caused by viral invasion

42
Q

animal viruses may be grown in what? (2)

A
  • living animals
  • embryonated eggs
43
Q

supernatant

A

denoting the liquid lying above a solid residue after crystallization, precipitation, centrifugation, or other process

44
Q

one-step growth curve experiment (6)

A
  1. infect cells in suspension
  2. incubate at 37ºC
  3. take samples at time of infection and then 1 hr intervals
  4. separate cells from culture supernatant
  5. make serial dilution of both cells and supernatant
  6. do plaque assay
45
Q

what is a common way to measure the amount of virus in a colution?

A

‘plaque forming units’ (PFU)

46
Q

multiplication of viruses: attachment

A

Virus binds to a specific receptor, and the presence or absence of these receptors largely dictates virus tropism - the ability of a virus to infect some cell types but not others

47
Q

multiplication of viruses: penetration (enveloped vs nonenvoloped)

A

The virus has to actually get inside the cell. Many have to get their genetic material across the cell membrane. Enveloped viruses do this by causing fusion between their membrane and that of the cell, while nonenveloped viruses either make a pore or actually disrupt the membrane

48
Q

multiplication of viruses: uncoating

A

The viral genome is tightly compacted within the capsid, so the capsid has to ‘uncoat’ in order for replication to proceed. Very little is known about this step.

49
Q

multiplication of viruses: transcription, translation, replication

A

The order in which these occurs depends on the nature of the viral genome (coming up). Basically, you have to make viral proteins, you have to make viral RNA, and you have to replicate the viral genome in order to make new viruses.

50
Q

multiplication of viruses: assembly

A

all of the pieces are put together to make new virus particles

51
Q

multiplication of viruses: release

A

The newly assembled viruses have to be released from cells some how. The cell can be lysed, the viruses can be secreted, or they can ‘bud’ from the cell surface.

52
Q

bacteriophage life cycles (6)

A
  1. attach to host cell receptor proteins
  2. inject genome through cell wall to cytoplasm
  3. replicate genome
  4. synthesize capsid proteins
  5. assemble progeny phage
  6. lyse cell wall to release progeny
53
Q

eukaryotic virus life cycle (2)

A
  1. attachment to host cell receptor
  2. fuses to the plasma membrane
54
Q

what does a virus receptor do? (4)

A
  • binds the virus to the cell
  • can just act to tether viruses
  • can trigger conformational changes in capsid or glycoprotein needed for entry
  • may send signals to cell
55
Q

tropism

A

the spectrum of tissues and cell types infected by a given virus

56
Q

tropism is often explained by the presence or absence of what?

A

the appropriate viral receptor

57
Q

which is more common, a virus binding to one receptor or more then one receptor?

A

only one receptor

58
Q

viral DNA must go where in the cell to replicate? why?

A

the cell nucleus to use the host polymerase (or replicate in cytoplasms with viral polymerase like Poxvirus)

59
Q

why must RNA viruses encode a viral polymerase?

A

host cells cannot read RNA to make more RNA

60
Q

why can (+) ssRNA be infectious?

A

(+) ssRNA can be translated to make viral proteins

61
Q

(-) ssRNA and retrovirus genomes must be _____ to be able to be translated

A

replicated

62
Q

(-) ssRNA must be converted into _____ (_____) by the RNA dependent RNA polymerase incorporated in the virion

A

(+) RNA; mRNA

63
Q

how different viruses replicate their genomes: DNA genomes

A

they are large viruses like pox-, herpes- and encode many of the enzymes required (like DNA polymerase) and are more autonomus

64
Q

how different viruses replicate their genomes: RNA genomes

A

encode their own RNA-dependent RNA polymerase which uses a complementary RNA template

65
Q

how different viruses replicate their genomes: retrovirus

A

copy (+) ssRNA genome into dsDNA, which is the template for new genome synthesis

66
Q

keypoint about RNA viruses

A

RNA-dependent polymerases lack proofreading so RNA viruses mutate quickly and often replicate faster

67
Q

why do DNA viruses mutate less often?

A

they have access to proofreading

68
Q

recombination

A

exchange of information between two genomes

69
Q

Animal (-) strand RNA viruses always carry into the host cytoplasm their own what? (2)

A

genome and polymerase protein

70
Q

Which of the following is NOT utilized to culture viruses?
- lab animals
- culture media
- embryonated eggs
- animal cel cultures
- bacterial cultures

A

culture media

71
Q

A clear are against a confluent “lawn” of bacteria is called a what?

A

pock

72
Q

The following steps occur during multiplication of the herpesviruses. Which if the third step?
- attachment
- biosynthesis
- penetration
- release of progenies
- uncoating

A

uncoating

73
Q

Which one of the steps does not occur during multiplication of a picornavirus?
- synthesis of + strands of RNA
- synthesis of - strands of RNA
- synthesis. of viral proteins
- synthesis of viral DNA
- none of the above

A

synthesis of - strands of RNA

MCB 4403 (7 decks)

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