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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)

A

TRUE

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
Q

Where does the viral envelope come from?

A

It is stolen from the host cell:

From the nuclear membrane, cytoplasmic membrane, golgi membrane, or ER membrane

26
Q

What are the two viral proteins primarily found in the envelope?

A

Glycoprotein (spikes)

Matrix protein

27
Q

What envelope proteins are highly antigenic, and involved in functions such as hemagglutination, receptor binding, and membrane fusion?

A

External glycoproteins

The spikes do everything

28
Q

What proteins in the envelope, regulate the influx and efflux of ions into the virus; maintaining the proper internal pH?

A

Channel proteins

29
Q

T/F: Some viruses have additional Fusion proteins within/on the lipid envelope

A

TRUE

helps the viral envelope fuse with the host cell

30
Q

What is the function of envelope matrix proteins?

A

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
Q

T/F: Virus envelopes help viruses survive better in the environment

A

FALSE

enveloped viruses are LESS stable than naked viruses

32
Q

T/F: the viral matrix protein is located between the viral nucleic acid and the capsid.

A

FALSE

It is located between the capsid and the envelope

33
Q

Which one of the following is NOT a component of viruses?

Nucleic acid
Capsid
Capsule
Envelope

A

Capsule

34
Q

T/F: Viral DNA is always circular

A

False

Can be linear as well

35
Q

What sense RNA is directly translated and used to synthesize viral protein?

A

Positive sense

Negative sense must first be converted to positive sense RNA

36
Q

What variations of viral RNA can you have in viruses?

A

single stranded vs double stranded

positive sense vs negative sense

segmented vs non segmented

37
Q

What are some mechanisms of genetic diversity that viruses may undergo?

A

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
Q

Which one of the following is NOT a mechanism of genetic diversity of viruses?

Reassortment
Point mutations
Recombination
Conjugation

A

Conjugation

39
Q

What are some important viral enzymes that are critical to infection, and their functions?

A
  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
Q

What is the function of viral nonstructural proteins?

A

May play roles within the infected cell during virus replication
or act in regulation of virus replication or virus assembly

41
Q

T/F: Nonstructural proteins are seen in extracellular virions

A

FALSE

These only appear when the virus is replicating in the host cell

42
Q

What is missing, that makes a virion incomplete?

A

No nucleic acid

Just an empty capsid

43
Q

What makes a virion defective?

A

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
Q

What is a pseudovirion?

A

A viral capsid with a NON-viral genome inside

RUSVM Virology Spring17 (23 decks)

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