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Microbiology 2 > Lecture 7: Viral Structure and Replication Part 1 > Flashcards

Lecture 7: Viral Structure and Replication Part 1 Flashcards

1
Q

What is a virus

A

small infectious agent, often below detection of light microscope

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2
Q

T or F: viruses are living cells

A

false- not living, lack ribosomes

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3
Q

viruses are __ the are completely dependent on __for reproduction

A

obligate intracellular parasites, dependent on living host cell

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4
Q

what is the difference between a virus and and the virion

A

virus is infected cell- alive
Virion is viral particle

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5
Q

what is a capsid

A

viral protein coat that surrounds the nuclei acid genome- allows attachment to host cells

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6
Q

what is an envelope and how is it acquired

A

lipid membrane, acquired by budding of through a cellular membrane

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7
Q

what are glycoproteins

A

anchored into the envelope, allows attachment to host cells

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8
Q

what is used for attachment to host cells with and without an envelope

A

with envelope: glycoproteins
Without envelope: capsid

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9
Q

___is a lipid bilayer derived from host cell

A

envelope

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10
Q

T or F: viral genomes do encode lipid synthetic machinery

A

false

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11
Q

viral components assemble at __because envelope needs viral proteins in it for cell attachment

A

cellular membrane

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12
Q

how do viruses replicate compared to bacteria

A

viruses: by assembly of preformed components into many particles

bacteria: binary fission

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13
Q

viral replication is __dependent

A

host cell dependent

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14
Q

describe the process of virus replication cycle

A
  1. Adhere to host cell via random collisions and electrostatic interactions
  2. Attach to specific receptors on host cell
  3. Enter cell via receptor mediated endocytosis
  4. Uncoating and release of genome in cytosol or nucleus
  5. Usurp host cell machinery to replicate
  6. Self assembly of new virions
    7.. Release from host cell by budding or cell lysis
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15
Q

t or f: viruses encode their own protein translation machinery

A

False- use host protein synthesis machinery- ribosomes

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16
Q

what is the only way to establish if infectious virus is present

A

viral culture

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17
Q

what does viral culture measure

A

whether infectious virions are present

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18
Q

what does PCR measure

A

whether viral DNA/RNA is present

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19
Q

what does antigen test measure

A

whether viral protein is present

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20
Q

what two things does a virus need to do to replicate

A
  1. Copy viral genome
  2. Make viral proteins
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21
Q

what type of genomes can viruses have

A

dsDNA, ssDNA, dsRNA, ssRNA

22
Q

DNA or RNA polymerases: prone to replication errors

A

RNA polymerase

23
Q

DNA or RNA polymerase: Host cell enzymes for replication

A

DNA polymerase

24
Q

DNA or RNA polymerase: virus encoded enzymes for replication

A

RNA polymerase

25
Q

RNA viruses use __dependent, __ polymerase, or __-

A

RNA, RNA, reverse transcriptase (RNA–> DNA)

26
Q

RNA or DNA polymerase: lack proofreading mechanisms

27
Q

__are ideal targets for anti-viral medications

A

virally-encoded enzymes

28
Q

DNA viruses use __for replication, fewer __introduced and therefore more genetically stable than RNA viruses

A

DNA, mutations

29
Q

What does acyclovir inhibit in herpes virus

A

DNA polymerase

30
Q

all viruses must make __that can be translated by host ribosomes. They are parasites of __

A

mRNA, host protein synthesis machinery

31
Q

DNA and mRNA with open reading frame is __sense

A

positive sense

32
Q

DNA and RNA complement of positive sense are __

A

negative sense

33
Q

positive or negative sense: immediately translate, ribosome ready

34
Q

positive or negative sense: extra RNA synthesis step prior to translation

35
Q

Baltimore classification puts ___in the center of classification

36
Q

what is group 1 Baltimore classification: dsDNA

A

dsDNA: genome is replicated by DNA dependent DNA polymerase. MRNA is transcribe by DNA dependent RNA polymerase

37
Q

what is an example of a virus that is classified as group 1 dsDNA

A

herpes simplex virus

38
Q

a dsDNA virus is spreading rapidly and causing severe disease in humans and animals including vesicular rash. Which of the following classes of drugs would be most effective:

A. Inhibitor of DNA-dependent DNA polymerase
B. Inhibitor of RNA dependent RNA polymerase
C. Acts on ion channels in plasma membrane, causing an influx of Cl- ions resulting in paralysis
D. Inhibitor of peptidoglycan synthesis
E. Inhibitor of ergosterol synthesis

A

A. Inhibitor of DNA-dependent DNA polymerase

39
Q

what is group 2 Baltimore classification: ssDNA

A

SsDNA: genome is replicated by DNA polymerase, DNA has to be double stranded to act as a template for mRNA synthesis so ssDNA is turned into dsDNA prior to mRNA synthesis

40
Q

What is an example of a virus classified as group 2 ssDNA

A

canine parvovirus

41
Q

what is group 3 Baltimore classification: dsRNA

A

dsRNA: genome is replicated by RNA-dependent RNA polymerase. Negative sense RNA strand blocks translation of positive sense so first have to use Rdrp to produce + mRNA before protein synthesis can occur

42
Q

What is an example of a virus classified as group 3 dsRNA

43
Q

what is Baltimore classification type 4: positive ssRNA

A

positive ssRNA: genome is replicated is replicated by RNA dependent RNA polymerase. Genomic RNA can be directly translated while also going through negative intermediate to synthesize more templates for mRNA

44
Q

what is an example of a virus classified as group 4 positive ssRNA

45
Q

What is Baltimore classification group 5: negative ssRNA

A

negative ssRNA: genome is replicated by RNA dependent RNA polymerase. Genomic RNA can’t be directly translated must produce + mRNA before synthesis

46
Q

What is an example of a virus classified as group 5 negative ssRNA

A

influenza virus

47
Q

negaitve ssRNA genomes need to bring in __

A

protein copy of RdRP to synthesize mRNA

48
Q

Positive ssRNA genomes do not require __

A

protein copy of RdRp because genomic viral RNA can be directly translated directly to make the RdRp in the host cell

49
Q

what is Baltimore classification group 6: positive ssRNA

A

genome is replicated by reverse transcriptase (RNA to DNA) which is then integrated into the host genome. MRNA is synthesized from integrated viral DNA

50
Q

What is an example of a virus classified as group 6 positive ssRNA

51
Q

what is Baltimore classification group 7: gapped dsDNA

A

genome is replicated by DNA polymerase and reverse transcriptase. SsDNA has to be repaired first into dsDNA before mRNA synthesis and protein production

52
Q

What is an example of a virus that is classified as group 7 gapped dsDNA

A

hepatitis B virus

Microbiology 2 (24 decks)

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