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Microbio 2302 > Ch.13 Viruses, Viroids & Prions Part 2 > Flashcards

Ch.13 Viruses, Viroids & Prions Part 2 Flashcards

1
Q

what are the steps to animal virus infection?

A
  1. attachment
  2. Entry
  3. Uncoating
  4. synthesis & replication
  5. Assembly
  6. Release
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2
Q

What occurs in attachment in an animal virus?

A

to host protein, & glycoprotein receptor sites

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3
Q

what occurs in the entry step in animal virus infection?

A

fusion (enveloped viruses)

receptor-mediated endocytosis

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4
Q

what occurs in the uncoating step in animal virus infection?

A

separation of the genome of the internalized virus from its capsid

can occur at the cell membrane or the nuclear membrane

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5
Q

what do animal viruses use to form in the host cytoplasm to form proteins?

A

ribosomes

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6
Q

where does the assembly of new virions (capsid, genome) occur?

A

in the cytoplasm or nucleus

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7
Q

how are virions released from the host?

A

lysis or budding

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8
Q

where are envelope proteins inserted into?

A

into the plasma membrane or organelle membrane

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9
Q

where does genome replication occur in DNA viruses?

A

nucleus

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10
Q

where does the synthesis of viral protein occur in DNA viruses?

A

outside of nucleus

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11
Q

where do viral proteins enter in DNA viruses?

A

into nucleus

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12
Q

where does viral assembly occur in DNA viruses?

A

nucleus

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13
Q

In Rna viruses where does genome replication, synthesis of viral proteins, and viral assembly all occur?

A

outside of the nucleus

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14
Q

DNA viruses in the multiplication of animal viruses utilize what?

A

utilize the host replication machinery (DNA polymerase)

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15
Q

DNA virus genome can serve as

A

a template for DNA synthesis and transcription

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16
Q

what do non-retroviral RNA viruses possess?

A

RNA-dependent
RNA Polymerase (RDRP)

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17
Q

Using the RDRP genome it can serve as a template for?

A

translation in (+) ss RNA viruses

synthesis of mRNA in (-) ss RNA viruses

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18
Q

what do retroviruses possess?

A

reverse transcriptase (RT)

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19
Q

Using reverse transcriptase, the genome can serve as a template for?

A

DNA synthesis

20
Q

steps to DNA virus infection:

A

1.Attachemnt: virion attaches to host cell

  1. Entry and Uncoating: The virion enters the cell and its DNA is uncoated
  2. A portion of viral DNA is transcribed, producing mRNA that encodes “early” viral proteins
  3. Biosynthesis: viral DNA is replicated and some viral proteins are made
  4. Late translation: capsid proteins are synthesized

6.Maturation: Virions mature

  1. Release: virions are released
21
Q

steps to RNA virus replication:

A
  1. attachment
  2. entry and uncoating
  3. RNA replication by viral RNA-dependent RNA Polymerase
  4. Translation and synthesis of viral proteins
  5. maturation & release
22
Q

ssRNA or + sense strand

A

picornviriade

  1. –strand is transcribes from + viral genome
  2. mRNA is transcribed from the - strand
  3. capsid protein forms & + strand
23
Q

ssRNA or - antisense strand

A

Rhabdoviridae

  1. the + strand (mRNA) must be transcribed from the - viral genome before proteins can be synthesized
  2. additional - strands are transcribed from mRNA

3.Capsid protein forms & - strands are incorporated into capsid

24
Q

dsRNA or + sense strand with - or antisense strand

A

Reoviridae

1.mRNA is produced inside the capsid and released into the cytoplasm of the host

  1. Capsid proteins and RNA-dependent RNA polymerase form
    RNA polymerase initiates the production of - strands. The mRNA and - strands form the dsRNA that is incorporated as a new viral genome
25
Q

retrovirus replication steps:

A
  1. an enveloped RNA virus enters by fusion
    *has 2 identical (+) RNA strands
    * infects T helper cells of the immune system
  2. uncoating releases RNA genome & viral enzymes, including reverse transcriptase to copy viral RNA to form dsDNA
  3. DNA integrates into the host genome; forming a provirus(intergrase)
  4. may stay in a persistent state while a cell is dividing
  5. provirus may be transcribed into RNA; and translated into viral proteins
  6. synthesized glycoproteins inserted into the host cell membrane; virus assembly and exit by budding
26
Q

Bacteriophage viral multiplication

A
  1. Attachment: tail fibers attached to cell wall proteins
  2. Entry: viral DNA is injected into the host cell
  3. uncoating: Not required
  4. biosynthesis: in cytoplasm
  5. chronic infection: lysogeny
  6. release: host cell is lysed
27
Q

Animal viral replication:

A
  1. Attachment: sites are plasma membrane and glycoproteins
  2. entry: capsid enters by receptor-mediated endocytosis or fusion
  3. uncoating: enzymatic removal of capsid proteins

4:biosytheis: in the nucleus (DNA viruses or cytoplasm (RNA virus)

  1. chronic infection: latency; slow viral infections; cancer
  2. release: enveloped viruses bud out; nonenveloped viruses rupture the plasma membrane
28
Q

what are prions?

A

are proteins that infect animals; they have no nucleic acid component

29
Q

what do prions cause?

A

degenerative brain disease (“mad cow” disease)

Creutzfield-Jacob disease in humans

scapie

kuru

30
Q

how are prions transmitted?

A

in food, prepared from infected animals

31
Q

what does prion disease do?

A

converts a normal brain cell glycoprotein (Prp^c) into an infectious form PrP^sc

PrP^Sc molecules accumulate in the brain, forming plaques (cavities)

32
Q

what are prions resistant to?

A

physical & chemical agents

33
Q

what are viroids?

A

are not viruses

are naked RNA molecules that lack a capsid

RNA does not encode for proteins (300-400) nucleotides long

34
Q

what do viroids infect?

A

plants

35
Q

how are viroids replicated?

A

by host RNA polymerase

36
Q

what do some viroids have?

A

catalytic ability

37
Q

what are latent viral infections?

A

virus that infects host cell but does NOT cause disease; can remain in a dormant state for long periods

38
Q

what can activate a latent infection?

A

Immunosuppression or stress

39
Q

what are some examples of latent infections?

A

oncogenic viruses

herpes viruses

chicken pox(shingles)

40
Q

what are persistent(chronic) viral infections?

A

occur gradually over a long period;
typically are fatal

41
Q

what is continuously released in persistent(chronic) viral infections?

A

viruses

42
Q

examples of persistent(chronic) viral infections?

A

HIV-1, 2

papillomavirus

Hepatitis B Virus

43
Q

describes lytic cycle:

A

t even phages

are virulent

phage quickly replicates killing the host cell(lytic burst)

44
Q

describe the lysogenic cycle:

A

lambda phage

temperate phages

do not necessarily kill the host immediately

integrates into cell chromosomes as a prophage

can reactivate to become lytic

environmental cues dictate when lysogeny converts to the lytic cycle

45
Q

The lytic cycle of phage T4

A
  1. attachment: to specific cell surface proteins
  2. Penetration: viral nucleic acid entering cell/ degradation of host DNA
  3. Biosynthesis: Viral DNA & viral proteins

The eclipse period between the degradation of host DNA and maturation

  1. Maturation
  2. Release: lysis of host cell wall by lysozyme
46
Q

Lysogenic viral DNA integrating into the host genome is what?

A

prophage

47
Q

transduction may result in what?

A

phage conversion

Microbio 2302 (15 decks)

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