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HMB202 > Viruses > Flashcards

Viruses Flashcards

1
Q

Intracellular state

A

capsid removed, only nucleic acid

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2
Q

Extracellular state

A

virion, capsid surrounding nucleic acid, phospholipid envelope

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3
Q

What is the capsid

A

protein coat that protects nucleic acid

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4
Q

What is nucleocapsid

A

capsid + nucleic acid

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5
Q

5 classes of viruses

A

bacterial (bacteriophage), archaeal, animal, plant, other

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6
Q

positive vs. negative polarity

A

positive same orientation as it mRNA, negative complementary orientation to mRNA

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7
Q

3 shapes of viruses

A

helical, polyhedral, complex

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8
Q

What is the capsomere

A

subunit of the capsid with same or diff types of proteins

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9
Q

How is the length and diameter of viruses determined

A

Length: nucleic acid length

Diameter: width of capsomere

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10
Q

What is the matrix protein

A

internal layer of envelope for extra protection

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11
Q

What is the envelope composed of

A

acquired from host cell - phospholipid bilayer and proteins such as glycoproteins

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12
Q

naked vs. enveloped virus

A

capsid + nucleic acid

envelope additional

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13
Q

2 types of nucleocapsids

A

helical rod shaped viruses - length and width measurement

icosahedral spherical viruses - most efficient energetical arrangement of subunits

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14
Q

Role of lysozyme in bacteria

A

makes hole in peptidoglycan in cell wall to lyse cell or allow nucleic acid to enter

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15
Q

Role of neuroaminidase

A

cleave glycosidic bonds to allow liberation exocytosis of viruses

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16
Q

Rate plant, bacteria, animal viruses in their efficiency to grow

A

bacterial, animal, plant

17
Q

What is confluency

A

% of surface covered by cells (higher = better)

18
Q

5 phases of viral replication

A
  1. Attachment - virus attach to host cell
  2. Entry - penetration of virion or nucleic acid
  3. Synthesis - viral nucleic acid and protein made by cell metabolism (early and late phase proteins)
  4. Assembly - capsids and viral genome packaged into mature virions
  5. Release - virions leave cell
19
Q

What are early vs late stage proteins

A

Early: polymerase and genomic DNA (catalytic), smaller amount

Late: capsomere, assembly proteins, membrane viral rafts, larger amount

20
Q

3 mechanisms of viral entry

A

direct penetration, membrane fusion, endocytosis (double membrane bound)

21
Q

What makes up the latent phase

A

eclipse + maturation

22
Q

Why does viral load decrease when it first enters cell

A

Goes from extra to intra cellular state virus in cell as free nucleic acid not a virion

23
Q

How does bacteriophage T4 infect cells

A

virions attach cells via tail fibres, fibres retract and tail core lysozyme forms pores in peptidoglycan, viral DNA enters cytoplasm

24
Q

What are 2 ways that eukaryotic and prokaryotic cells prevent viral attack (2 each)

A

Immune defense, RNA interference

CRISPR, restriction modification enzyme systems (dsDNA viruses only) that cut viral DNA or modify host DNA to prevent cleavage and incorporation of viral DNA

25
Q

What are 2 ways that viruses evade our restriction modification system

A

chemical modifications on viral DNA, production of proteins that inhibit host system

26
Q

Name the 7 classes of Baltimore classification scheme

A
  1. dsDNA
  2. ssDNA
  3. dsRNA
  4. ssRNA (+)
  5. ssRNA (-)
  6. Retroviruses
  7. dsDNA that replicate through RNA intermediate
27
Q

How does each class get to mRNA (+)

  1. dsDNA
  2. ssDNA
  3. dsRNA
  4. ssRNA (+)
  5. ssRNA (-)
  6. Retroviruses
  7. dsDNA that replicate through RNA intermediate
A
  1. DNA dependent RNA poly
  2. replication to dsDNA intermediate then DNA dependent RNA poly
  3. RNA dependent RNA poly
  4. Used directly
  5. RNA dependent RNA poly
  6. RNA dependent DNA polymerase to dsDNA intermediate then DNA dependent RNA polymerase
  7. DNA dependent RNA polymerase to ssRNA then RNA dependent DNA polymerase to dsDNA then DNA dependent RNA polymerase
28
Q

Where do DNA vs RNA viruses replicate

A

nucleus vs cytosol

29
Q

Which strand gets translated when making positive mRNA

A

antisense strand (negative strand)

30
Q

Lytic vs lysogenic cycle

A

Lytic: circular nucleic acid gets translated intro virions

Lysogenic: circular nucleic acid gets integrated into host DNA via recombination

31
Q

What initiates lysogenic to lytic change

A

UV light, chemicals

32
Q

What is induction

A

viral nucleic acid excised from host genome to undergo lytic cycle

33
Q

What is prophage

A

host DNA and bacterial viral genome integrated together, translation repressed by 2 proteins encoded by phage genes

34
Q

difference between animal vs prokaryotic viruses

A

entire virion enters cell, not just the nucleic acid

much more enveloped animal viruses

35
Q

4 consequences of viral infection in animal cells

A
  1. persistent infection - release of virions does not lyse cell
  2. latent infection - delay from infection and lytic events
  3. transformation - normal cell to neoplastic tumour cell
  4. cell fusion - cells become one with many nuclei (genomic stability of host genome)
36
Q

How do viruses leave the cell

A

budding - recognize viral glycoproteins (lipid rafts) and use host microtubule and microfilaments to bud

37
Q

What are retroviruses and what do they contain

A

2 copies of positive ssDNA integrated at 2 parts of the genome

enveloped with a reverse transcriptase, integrase, and protease

virion contains tRNA from host

38
Q

What genes do retroviruses have and what is the role

A

gag: structural proteins
pol: reverse transcriptase and integrase
env: envelope proteins

39
Q

What are 7 steps of retrovirus infection cycle

A
  1. entrance
  2. removal of envelope
  3. reverse transcribe 1 of 2 RNA genome
  4. integrate viral DNA into genome
  5. transcribe viral DNA
  6. assembly and packaging of genomic RNA
  7. budding and release of virions

HMB202 (7 decks)

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