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Fpathogens > 17 - Virology > Flashcards

17 - Virology Flashcards

1
Q

Viruses are the smallest _______________

A

self-replicating organisms

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2
Q

They have no ___________, they are obligated to invade cells and hijack the cellular machinery

A

independent metabolism

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3
Q

Viruses can consist solely of a small segment of ________________ encased in a simple _____________

A

nucleic acid

protein shell

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4
Q

T or F: There is an ongoing debate if viruses constitute life or not

A

T

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5
Q

Positive-sense viral RNA is similar to _____ and can immediately be _______ by the host cell

A

mRNA

translated

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6
Q

T or F: Purified RNA of a positive-sense virus can directly cause infection, although, it may be less infectious than the whole virus particle

A

T

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7
Q

Negative-sense viral RNA is complementary to the _______ and thus must be converted to ____________ by a RNA ___________ before translation.
Purified RNA is not infectious by itself

A

mRNA
positive-sense RNA
polymerase

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8
Q

Viruses containing ambisense single-stranded RNA genomes are grouped under ________________________
Ambisense means that the virus resembles a __________ sense RNA virus, however they can also translate genes from the _______ strand

A

negative sense single-stranded RNA viruses

negative

positive

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9
Q

Give the characteristics (3) of enveloped viruses:

A
  • have lipid-bilayer membranes
  • impermeable barrier between their genomes and the outside environment
  • ex: HIV, influenza
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10
Q

Give the characteristics (3) of non-enveloped viruses:

A
  • no membranes
  • no barrier, therefore require a tightly packed protein shell to exclude nucleases or other sources of genetic damage
  • ex: poliovirus / papillomavirus
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11
Q

The virus binds to the surface of receptive host cells and entry is initiated by: (3)

A
  • inducing conformational changes in the virus that lead to association with other receptors, membrane fusion, and penetration
  • transmit signals through the membrane prepares the cell for invasion
  • induction of the endocytic pathway
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12
Q

T or F: viruses can only infect cells to which they can bind

A

T

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13
Q

The virus triggers the penetration process and enters the __________

A

cytosol

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14
Q

DNA viruses are transported to the nucleus for genome __________ or __________

A

uncoating or replication

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15
Q

T or F: Several viruses have developed mechanisms to allow them to deliver their DNA to the nucleus?

A

T

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16
Q

RNA viruses may be translated in the_______

A

cytosol

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17
Q

Viruses rely on functions provided by their _______

A

host cells

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18
Q

Almost all viruses encode and express unique ________ including ________

A

proteins

enzymes

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19
Q

RNA viruses must replicate their genomes one of 2 unique ways:

A

1) RNA-dependent-RNA synthesis (RNA replication)

2) RNA-dependent-DNA synthesis (reverse transcription) followed by DNA replication and transcription (ex: retroviruses)

20
Q

All viruses must eventually express their genes as _______________ early in infection to make essential viral ___________

A

functional mRNA

proteins

21
Q

mRNA is always defined as _____________ and its complement is negative-sense

A

positive sense RNA

22
Q

Each type of virus will have different strategies to make mRNA dependent upon their starting ___________

A

genetic material

23
Q

Each of the viral replication pathways will require different enzymes : if it is an enzyme that the host encodes the virus will use the ___________ enzyme. If it is an enzyme that is not included in the host biology the virus must _______________

A

host encoded

encode its own enzyme

24
Q

What is the issue with the polymerases that catalyze RNA replication and reverse transcription?

A

-They have minimal proofreading activities

25
Q

Name the 4 important foodborne viruses:

A

1- Poliovirus
2- Hepatitis A virus
3- Norovirus
4- Rotaviruses

26
Q

RNA-dependent RNA polymerases (RdRp’s) and reverse transcriptases have an error rate that is _____ orders of magnitude higher than DNA-dependent DNA polymerases

A

three

27
Q

RNA viruses evolve at a much faster rate than their ____

A

host

*this means that the viruses sometimes can escape from host produced neutralizing antibody

28
Q

____________ are transported to a point in the host cell where they can be assembled into a viral particle

A

Macromolecules

29
Q

Most viruses rely on the ____________ for biosynthesis of their macromolecules as well as for intracellular sorting and delivery of macromolecules to the site of virion assembly

A

eukaryotic cell

30
Q

Because the same sorting mechanisms that the cell uses for it’s own molecules is used the viral macromolecules must also possess similar ___________

A

targeting signals

31
Q

Explain the main steps in virus assembly:

A
  • proteins must be transported to the plasma membrane must travel through the secretory pathway of the cell
  • they associate with the endoplasmic reticulum and are translocated across via a proteinaceous pore
  • these proteins can then be transported to the golgi complex and onto to the plasma membrane unless they contain AA motifs that localize them to another location
32
Q

Intracellular transport occurs in ______________

A

coated vesicles

33
Q

Non-enveloped viruses can assemble in the ________ or the ___________

A

cytoplasm

nucleus

34
Q

For non-enveloped viruses structural proteins must be retained at the _________________ where assembly occurs

A

subcellular domain

35
Q

Enveloped viruses must acquire a ______________ from a host cell membrane during assembly

A

lipid bilayer

36
Q

Explain the virus assembly for a non-enveloped virus:

A

1- macromolecules assemble into empty capsids
2- viral DNA is inserted into the structure via a packaging sequence at one end of the genome
3- precursor core proteins are also packaged into the empty capsid along with DNA
4- proteolytic cleavage of the precursor proteins by proteinase yields the mature (infectious) virion

37
Q

What are the 3 pathways of enveloped virus assembly ?

A

1- proteins are transported to plasma membrane and assembly of the capsid and envelopment occurs simultaneously
2- capsid assembly occurs in the cytoplasm and then the virus buds from the plasma membrane and gets its envelope
3- capsid assembly occurs in the cytoplasm and gets its envelope from the ER and is exported via exocytosis

38
Q

Glycoproteins are transported to the preferred lipid bilayer of whichever virus is involved: (2)

A
  • plasma membrane

- endoplasmic reticulum

39
Q

Viral capsid develops elsewhere in the cell, nucleic acids are packaged in the capsid and transported, in ______________, to the area where the envelop will be acquired

A

endosomal vesicles

40
Q

In the case of the ER the enveloped virion is transported to the plasma membrane via the ______________

A

transport vesicle

41
Q

T or F: enteric viruses are an important cause of foodborne illness in Canada and other countries

A

T

42
Q

Foodborne enteric viruses are hard to ___________ and hard to recover from contaminated foods (most are not __________)

A

detect

culturable

43
Q

What happens to foodborne enteric viruses in food systems?

A

they do not multiply in food systems, some die off rapidly during food storage and preservation

44
Q

Are foodborne enteric viruses excreted in high numbers in human feces?

A

yes

45
Q

What can kill enteric viruses:

A
  • pasteurization
  • heat
  • irradiation
46
Q

T or F: foodborne enteric viruses can multiply outside the human body

A

F, they require human cells to multiply

Fpathogens (23 decks)

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