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RUSVM Virology Spring17 > (Final) Virus structure > Flashcards

(Final) Virus structure Flashcards

1
Q

What is the smallest virus of animals?

A

Porcine circovirus type 1

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2
Q

What is the largest virus of animals?

A

Pox virus

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3
Q

What shape is the rabies virus?

A

bullet shape

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4
Q

What shape is the pox virus?

A

Brick shape

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5
Q

What does it mean if a virus is pleomorphic?

A

It has the ability to alter their shape or size

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6
Q

What is a bacteriophage?

A

Tadpole shaped virus that infects bacteria

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7
Q

What kind of microscope is used to see viruses? What kind of staining is commonly used?

A

Transmission Electron microscope

negative staining

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8
Q

What is cryo-electron microscopy?

A

Liquid nitrogen is used to freeze the sample, allowing it to be observed in their native environment
*finer resolution/clearer image with sample intact

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9
Q

Besides electron microscopy, what are two other method to dectect/visualize viruses?

A

E-ray crystallographic method
*even more detailed image

Nuclear magnetic resonance method

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10
Q

What is the basic structure of a virus?

A

DNA or RNA wrapped in a capsid (protein coat) - wrapped in an envelope (bubble of fat)

The envelope can have glycoprotein spikes

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11
Q

What are the two types of capsid symmetry?

A

Polyhedral

Helical virus

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12
Q

T/F: Animal viruses that have capsids with a helical symmetry are most often enveloped

A

TRUE

*but there can be naked viruses of PLANTS that have a helical symmetry

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13
Q

Most viruses have one capsid, what is the virus that is an exception with a double layered capsid?

A

Reoviruses

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14
Q

What is the basic subunit protein in the capside of a virus?

A

A capsomere

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15
Q

Capsid + virus DNA or RNA = _________

A

Nucleocapsid

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16
Q

What are the components of the icosahedral capsid?

A 
12 pentons (12 corners) **always constant**
20 facets (Hexons - this numer will vary)
30 edges
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17
Q

What is the triangulation number of a virus?

A

It denotes the relationship between the number of pentagons and hexagons of the icosahedron

T= (h^2 + h)(k +k^2)
h and k are directions

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18
Q

T/F: the number of pentons is ALWAYS constant (12)

19
Q

What virus has the simplest icosahedron, with a T=1, triangulation number?

A

Parvovirus

The capsid consists of 60 copies of CP proteins

20
Q

What virus has a more complex symmetry with an outer capsid that has T=13 icosahedral symmetry, and inner capsid that has a T=2 icosahedral symmetry?

A

REOVIRIDAE

**only viruses with 2 capsids

21
Q

What is the symmetry of the pox virus?

A

It is very COMPLEX - so it is neither icosahedral or helical

22
Q

What are the functions of the viral capsid?

A
  1. structural symmetry
  2. Encases and protects the viral nucleic acid from enzymes, chemicals, and physical conditions
  3. functions in attaching to the host cell (receptor proteins)
  4. Once inside the host hell - it helps deliver the nucleic acid to the replication site
  5. functions in packaging of newly replicated virus
23
Q

T/F: Viral capsids have antigenic proteins

A

TRUE

these can be targeted for tx or vaccines

24
Q

What is a viral envelope composed of? What is the fuction?

A

Lipid bilayer with embedded proteins

Facilitaes virus entry into the host cell and may help the virus to adapt fast and evade the host immune system

25
Where does the viral envelope come from?
It is stolen from the host cell: | From the nuclear membrane, cytoplasmic membrane, golgi membrane, or ER membrane
26
What are the two viral proteins primarily found in the envelope?
Glycoprotein (spikes) | Matrix protein
27
What envelope proteins are highly antigenic, and involved in functions such as hemagglutination, receptor binding, and membrane fusion?
External glycoproteins The spikes do everything
28
What proteins in the envelope, regulate the influx and efflux of ions into the virus; maintaining the proper internal pH?
Channel proteins
29
T/F: Some viruses have additional Fusion proteins within/on the lipid envelope
TRUE helps the viral envelope fuse with the host cell
30
What is the function of envelope matrix proteins?
Plays a crucial role in virus assembly. Attaches to the inside of the host cell - where glycoproteins are along the outside, to act as indicators for newly replicated viral DNA/RNA to find the glycoproteins *also stabilize the lipid envelope
31
T/F: Virus envelopes help viruses survive better in the environment
FALSE enveloped viruses are LESS stable than naked viruses
32
T/F: the viral matrix protein is located between the viral nucleic acid and the capsid.
FALSE It is located between the capsid and the envelope
33
Which one of the following is NOT a component of viruses? Nucleic acid Capsid Capsule Envelope
Capsule
34
T/F: Viral DNA is always circular
False Can be linear as well
35
What sense RNA is directly translated and used to synthesize viral protein?
Positive sense Negative sense must first be converted to positive sense RNA
36
What variations of viral RNA can you have in viruses?
single stranded vs double stranded positive sense vs negative sense segmented vs non segmented
37
What are some mechanisms of genetic diversity that viruses may undergo?
Antigenic drift = point mutations (can influence the dx, vaccines etc) Antigenic shift: Recombination = Mixture of two different viruses - making a new one (**occurs in viruses with a SINGLE gene segement) Reassortment = (**ocurrs in viruses with multiple segements) Swapping of genome segments between viruses shift will result in a drastic change in the antigenicity of the virus
38
Which one of the following is NOT a mechanism of genetic diversity of viruses? Reassortment Point mutations Recombination Conjugation
Conjugation
39
What are some important viral enzymes that are critical to infection, and their functions?
1. Retroviral integrase (IN) - enzyme produced by a retrovirus hat enables its genetic material to be intergrated into the DNA of the infected cell 2. Reverse transcriptase (RT): enzyme used to generate complementary DNA (cDNA) from a RNA template 3. Nucleic acid polymerases: Viral genome replication
40
What is the function of viral nonstructural proteins?
May play roles within the infected cell during virus replication or act in regulation of virus replication or virus assembly
41
T/F: Nonstructural proteins are seen in extracellular virions
FALSE These only appear when the virus is replicating in the host cell
42
What is missing, that makes a virion incomplete?
No nucleic acid Just an empty capsid
43
What makes a virion defective?
If it cannot replicate because: It lacks a full complement or copy of viral genes Due to: mutations or errors in the production or the assembly of viruses
44
What is a pseudovirion?
A viral capsid with a NON-viral genome inside

RUSVM Virology Spring17 (23 decks)

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