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RUSVM Virology > Morphology of Viruses > Flashcards

Morphology of Viruses Flashcards

1
Q

Smallest Viruses

A

Porcine Circovirus type-1 (17nm)

Parvovirus (18nm)

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2
Q

Largest Viruses

A

Pandoravirus (400nm)

Poxvirus (200x300nm)

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3
Q

Pleomorphism

A

Ability of some viruses to alter their shape or size

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4
Q

Most viruses are _______ or __________ shaped.

A

Most viruses are rod or spherical shaped.

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5
Q

Common methods used to deterime the morphology of viruses:

A

Electron Microscopy (EM)

Cryo-Electron Microscopy (Cryo-EM)

X-Ray Crystallographic Method

Nuclear Magnetic Resonance (NMR)

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6
Q

_____________ method requires negative staining with electron dense material such as Uranyl Acetate or Phosphotungstate.

A

Electron Microscopy (EM) method requires negative staining with electron dense material such as Uranyl Acetate or Phosphotungstate.

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7
Q

Resolution range for electron microscopy

A

50-75 angstroms

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8
Q

________________ method allows the observation of biological specimens in thier native environment (not fixed or stained in any way)

A

Cryo-Electron Microscopy (Cryo-EM) method allows the observation of biological specimens in thier native environment (not fixed or stained in any way)

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9
Q

Resolution range for Cryo-Electron Microscopy

A

3.3 to 20 angstroms

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10
Q

Explain the X-Ray Crystallographic method process

A
  1. Virus or viral protein is crystalized
  2. X-ray
  3. Deflection mesasured to form electron density map
  4. Protein model created
  5. Reconstruction of virus structure
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11
Q

Capsid

A

Protein shell of a virus that encases/ envelopes the viral nucleic acid or genome

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12
Q

The capsid is made up of ______ held together by covalent bonds

A

The capsid is made up of capsomeres held together by covalent bonds

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13
Q

Viruses have one capsid, except for _____________ which have a double layered capsid

A

Viruses have one capsid, except for Reoviruses which have a double layered capsid

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14
Q

Capsomere

A

Basic subunit protein in the capsid of a virus

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15
Q

Nucleocapsid

A

Capsid + Virus Nucleic Acid/Genome

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16
Q

Common capsid symmetries

A

Helical Symmetry

Cubic/ Icosahedral Symmetry

Complex

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17
Q

Incomplete virions cannot form ____________ symmetry.

A

Incomplete virions cannot form helical symmetry.

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18
Q

Helical nucleocapsids of animals are enclosed by ____________

A

Helical nucleocapsids of animals are enclosed by lipoprotein envelope

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19
Q

Naked helical nucleocapsids are common among _______ viruses.

A

Naked helical nucleocapsids are common among plant viruses.

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20
Q

Icosahedral viruses always have ________ corners

A

Icosahedral viruses always have 12 corners

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21
Q

Two types of capsomers present in icosahedral capsid

A

Pentagonal Capsomers

Hexagonal Capsomers

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22
Q

Pentons make up the (vertices/facets)

A

Pentons make up the (vertices/facets)

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23
Q

Hexons make up the (vertices/facets)

A

Hexons make up the (vertices/facets)​

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24
Q

Triangulation Number (T-Number)

A

Describes the relation between the number of pentagons and hexagons of the icosahedron.

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25
Q

The (larger/smaller) the T-Number the more hexagons are present relative to the pentagons.

A

The (larger/smaller) the T-Number the more hexagons are present relative to the pentagons.

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26
Q

T- Number Equation

A

T = H2 + h * k + k2

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27
Q

________ has a T = 1, simplest icosahedron

A

Parvovirus has a T = 1, simplest icosahedron

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28
Q

Functions of viral capsid

A
  1. Structural symmetry
  2. Encase and protect viral nucleic acid
  3. Facilitate attachment of the virus to specific receptors on the susceptible host cells
  4. Interact with host cell membrane to form envelope
  5. Uncoat genome
  6. Transport viral genome
  7. Recognize and package nucleic acid genome
29
Q

Viral envelope

A

Lipid bilayer with embedded proteins, facilitates virus entry into host cells and may also help the virus to adapt fast and evade host immune system

30
Q

Explain how a virus acquires its envelope

A

Acquired by budding of viral nucleocapsid through a cellular membrane

31
Q

Two kinds of viral proteins found in the envelope

A

Glycoprotein

Matrix Protein

32
Q

Glycoprotein

A

Anchored in the lipid bilayer by hydrophobic bonds, spikes seen on the virus surface

33
Q

External Glycoprotein

A

Anchored in the envelope by a single transmembrane domain and a shorter internal tail

Antigens of the virus and involved in hemagglutination, receptor binding, antigenicity and membrane fusion

34
Q

Channel Proteins

A

Hydrophobic proteins that form a protein lined channel through the envelope

Alter permeability of the membrane and important in modifying the internal envrionment of the virus

35
Q

Fusion proteins

A

Channel proteins that facilitate attachment and entrance of viral contents to enter host cell

36
Q

Two kinds of fusion proteins

A

pH Independent

pH Dependent

37
Q

HIV and Measles are examples of pH (independent/dependent) fusion proteins.

A

HIV and Measles are examples of pH (independent/dependent) fusion proteins.

38
Q

HA of the influenza virus is an example of pH (independent/dependent) fusion proteins.

A

HA of the influenza virus is an example of pH (independent/dependent) fusion proteins.

39
Q

Matrix Protein

A

Proteins that lnk the internal nucleocapsid to the lipid membrane envelope

Recognition site of nucleocapsid at the plasma membrane and mediates the encapsidation of the RNA nucleoprotein cores into the membrane

40
Q

________ proteins play a crucial role in virus assembly

A

Matrix proteins play a crucial role in virus assembly

41
Q

(Enveloped/Non-Enveloped) viruses are easy to sterilze and cannot survive for long periods in the environment

A

(Enveloped/Non-Enveloped) viruses are easy to sterilze and cannot survive for long periods in the environment

42
Q

(+/-) Sense RNA viruses have infectious genomes

A

(+/-) Sense RNA viruses have infectious genomes

43
Q

+ Sense RNA Genome

A

Similar to mRNA and thus can be immediately translated by the host cell

44
Q
  • Sense RNA Genome
A

Complementary to mRNA and thus must be converted to + sense before translation

45
Q

RNA Polymerase

A

Converts - Sense RNA to +Sense RNA

46
Q

Antigenic Drift

A

Changes in the virus that arise from point mutations, may cause change in antigenicity

47
Q

Processes of Antigenic Shift

A

Recombination

Reassortment

48
Q

Recombination

A

Exchange of nucleotide sequences between different, but usually closely related, viruses during replication

49
Q

Reassortment

A

Exchange of segmented genomic segments

50
Q

Most important mechanism for high genetic diversity in viruses with segmented genome is _____________

A

Most important mechanism for high genetic diversity in viruses with segmented genome is Reassortment

51
Q

Viral _________ constitute up to 50-70% of the virion

A

Viral protein constitute up to 50-70% of the virion

52
Q

Two classes of virion proteins

A

Modified Proteins

Unmodified proteins

53
Q

(Modified/Unmodified) viral proteins are obtained by post-translational proteolytic cleavage of polyprotein.

A

(Modified/Unmodified) viral proteins are obtained by post-translational proteolytic cleavage of polyprotein.

54
Q

Lysins

A

Hydrolytic enzymes produced by bacteriophages to cleave the host cell wall

55
Q

Retroviral Integrase (IN)

A

Enzyme produced by a retrovirus that enables its genetic material to be integrated into the DNA of the infected cell

56
Q

Reverse Transcriptase (RT)

A

Enzyme used to generate complementary DNA (cDNA) from an RNA template

57
Q

Nucleic Acid Polymerase

A

Responsible for viral genome replication

58
Q

Structural Viral Proteins

A

Proteins the form the viral capsid

59
Q

Nonstructural Viral Proteins

A

Encoded by viral genome that are produced in the organisms they infect, but not packed into the virus particles

Play role within the infected cell during virus replication or act in regulation of virus replication or virus assembly

60
Q

Regulatory Proteins

A

Broad category of proteins that play indirect roles in the biological processes and activities of viruses

Regulate the expression of viral genes or are involved in modifying host cell functions

61
Q

Incomplete virions

A

Virion without nucleic acid

62
Q

Effective Virions

A

Virus that cannot replicate because it lacks full complement/ copy of viral genes

63
Q

Defective Viral Particles

A

Result from mutations or errors in the production or assembly of virions

64
Q

Replications of defective virions occurs only in mixed infection with a ___________.

A

Replications of defective virions occurs only in mixed infection with a helper virus.

65
Q

Helper Virus

A

Supplement the genetic deficiency and make defective viruses replicate progeny virions when they simultaneously infect host cell and defective viruses

66
Q

Defective Interfering Particle (DIP)

A

Defective virus can not replicate, but can interfere other congeneric mature virion enter the cells

67
Q

Pseudovirion

A

Contains non-viral genome within the viral capsid, look like ordinary viral particles but do not replicate

68
Q

Pseudotypes

A

Related viruses infect the same cell, the genome of one virus may be enclosed in the heterologous capsid of the second

RUSVM Virology (35 decks)

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