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Micro-EX2- Tye > Middleton - Virus Classification, structure & Replication > Flashcards

Middleton - Virus Classification, structure & Replication Flashcards

1
Q

What attributes classify viruses?

A
  • Virus particle structure
  • Genome
  • Replication
  • Serology
  • Stability
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2
Q

Virus is defined by the presence of a ________.

A

Nucleocapsid structure

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3
Q

What are the 3 types of structure the nucleocapsid can assume?

A
  • helical
  • pleomorphic
  • Icosahedral
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4
Q

Nucleocapsid is comprised of repeating protein subunits called __________.

A

Capsomeres

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5
Q

________ are virus modified cellular membranes acquired upon exit from host.

A

Envelopes

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6
Q

Size range of a virus?

A

18nm-300nm

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7
Q

Enveloped viruses may have nucleocapsids with _____________.

A

Different structures

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8
Q

What kinds of RNA are in the viral genome?

A
  • Double stranded

- Single stranded (+sense, -Sense & ambisense)

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9
Q

Central dogma

A

info flows from DNA downward.

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10
Q

What types of structures are found in the viral genome?

A
  • Linear
  • circular
  • segmented
  • diploid
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11
Q

What is needed to get replication started in viruses?

A

hairpin

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12
Q

What are the steps of Virus Replication?

A
  • Attachment
  • Entry
  • Transcription
  • Translation
  • Replication
  • Assembly
  • release
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13
Q

What two components are needed for attachment?

A

Cellular receptors

  • signaling molecules
  • cell adhesion
  • transport

Viral Transporters

  • Usually do not mimic cell receptor’s normal ligand
  • Typically spike-like projections on particle surface
  • May require a co-receptor
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14
Q

__________ can change receptor recognition.

A

Genetic engineering

  • Integrin RGD sequence = used by Ad, engineered into lambdaphage.
  • Pseudotyping particles = improve retroviral entry (VSV, Ebola & LCMV)
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15
Q

_______ ia a major determinant of virus tropism (Host range or hosts that virus will infect)

A

Attachment

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16
Q

Viruses can infect essentially all forms of life, but where do they draw the line in infection?

A

They don’t cross kingdoms or across more divergent hosts (Plants —> people)

17
Q

________ is a major factor in eradication of a virus.

A

Host range

18
Q

What are the 2 pathways of entry for a virus?

A
  • Receptor mediated endocytosis
  • Direct penetration of plasma membrane
  • methods of non enveloped viruses are not well understood (uses pores called picornavirus)
19
Q

How does entry work with a enveloped virus?

A
  1. Membrane fusion
  2. Receptor Conformational change (low pH)
  3. Uncoating
    - Nuclear Replication = Genome and remaining protein coat transported to the nuclear membrane
    - Cytoplasmic Replication = Release of genome into cytoplasm & Transportation of the genome into intracellular site of replication. *dsRNA viruses NEVER release their genomic material from the entering particle.
20
Q

What are the steps of virus Transcription?

A

1) Production of messenger RNA (mRNA) template for protein synthesis.
* THE GENOME OF (+) ssRNA can serve as mRNA!
* Production of new transcripts can occur later using (-) ssRNA.

21
Q

DNA viruses usually rely on ___________ during Transcription

A

Cellular RNA polymerases

22
Q

_________ & _________ viruses must bring their own polymerases into the cell during Transcription.

A

(-) ssRNA & dsRNA

23
Q

True or false - during translation, all viruses need the cell’s ribosomes to produce protein?

A

True - no exceptions!

24
Q

Where can viral protein production be regulated?

A

at the Transcript (mRNA) level or translation level

25
Q

During translation Structural proteins are found in _______ quantities.

A

High

26
Q

Durin translation, ____________ are only seen inside the infected cell.

A

Non-structural proteins

27
Q

What is the order of events in Genome Replication?

A

Hah! The order of events depends of the virus genome!

28
Q

What is unique to Genome Replication with (+)ssRNA?

A
  • Genome serves as template for translation

- Polymerase makes (-)ssRNA copy as template for new genomes.

29
Q

What is unique to Genome Replication with (-)ssRNA?

A
  • Virus particles must include the viral polymers
  • Polymerase makes messenger RNA for translation
  • Genome replicates through full-length (+)ssRNA intermediate.
30
Q

What is unique to Genome replication with dsRNA?

A
  • Virus particle includes viral polymerase
  • dsRNA induces innate immune response so genome stays inside particle.
  • mRNA synthesized in particle and exported to cytoplasm
  • mRNA serves as (+) strand in virus genome, (-) strand synthesized during assembly.
31
Q

What is unique to Genome replication with ssDNA & dsDNA?

A
  • Must gain access to nucleus!
  • Poxviruses are the exceptions
  • Prepare the cell for DNA replication
  • Ensure genome ends are copied

Micro-EX2- Tye (12 decks)

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