Virology L3
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Questions and Answers

What is the smallest known virus?

  • Pox virus
  • Ebola Virus
  • Porcine circovirus type 1 (correct)
  • Rotavirus

Which virus is the largest in size?

  • Rotavirus
  • Pox virus (correct)
  • Rabies virus
  • Tobacco mosaic virus

What does the term “pleomorphism” refer to in virology?

  • The ability of a virus to infect multiple species
  • The process by which viruses cause disease
  • The replication mechanism of viruses
  • The ability of a virus to alter its shape or size (correct)

Which virus has a filament-shaped structure?

<p>Ebola virus (C)</p> Signup and view all the answers

What is the characteristic shape of the rabies virus?

<p>Bullet-shaped (C)</p> Signup and view all the answers

Which virus is rod-shaped?

<p>Tobacco mosaic virus (A)</p> Signup and view all the answers

What is the shape of a bacteriophage?

<p>Tadpole-shaped</p> Signup and view all the answers

How is the shape of poxvirus described?

<p>Brick-shaped</p> Signup and view all the answers

List the common methods used to determine the morphology of viruses.

<p>Electron microscopy, Cryo-EM, X-ray crystallographic method and nuclear magnetic resonance (NMR)</p> Signup and view all the answers

What is the protein coat encasing a virus’s nucleic acid called?

<p>Capsid (C)</p> Signup and view all the answers

What are capsomeres?

<p>The basic subunits of the capsid in a virus (B)</p> Signup and view all the answers

Describe the layers of your “winter jacket” in the context of the morphology of a virus

<p>The envelope is the most outer layer of the virus, then the capsid, and finally the nucleic acid that’s encased within the capsid</p> Signup and view all the answers

Which virus is unique for having a double layered capsid?

<p>Reoviruses (D)</p> Signup and view all the answers

Which of the following techniques is NOT commonly used to determine virus morphology

<p>Gram staining (B)</p> Signup and view all the answers

What is the main function of the capsid of a virus?

<p>Encapsulate and protect the viral nucleic acid/genome (C)</p> Signup and view all the answers

What does the term nucleocapsid refer to in virology?

<p>The capsid and virus nucleic acid (DNA or RNA) combined (B)</p> Signup and view all the answers

How do viruses acquire an envelope?

<p>By budding through the host cell membrane (B)</p> Signup and view all the answers

Which type of capsid symmetry is found in all animal viruses with helical nucleocapsids?

<p>Helical (C)</p> Signup and view all the answers

What is unique about helical nucleocapsids in plant viruses?

<p>They are always naked, without a lipid envelope (D)</p> Signup and view all the answers

What are the two types of capsomeres in icosahedral capsid symmetry?

<p>Pentagonal capsomeres (pentons) and hexagonal capsomeres (hexons) (A)</p> Signup and view all the answers

How many pentons are always present in an icosahedral capsid?

<p>12 (B)</p> Signup and view all the answers

What is the formula to calculate the triangulation number (T-number) of an icosahedral capsid?

<p>T = h^2 + h x k + k^2</p> Signup and view all the answers

What is the T-number of the simplest icosahedral virus, such as parvovirus?

<p>T = 1 (A)</p> Signup and view all the answers

What are the T-numbers of the inner and outer capsid layers in Reoviridae?

<p>Inner: T=2, Outer: T=13</p> Signup and view all the answers

What characterizes complex capsid symmetry in viruses?

<p>Visions with several parts, each with separate shapes and symmetries (B)</p> Signup and view all the answers

Which virus is an example of complex symmetry?

<p>Poxvirus (C)</p> Signup and view all the answers

What type of virus typically contains complicated structures and exhibits complex symmetry?

<p>Bacteriophages (B)</p> Signup and view all the answers

How does the viral capsid protect the nucleic acid of a virus?

<p>By providing a barrier against enzymes, chemicals, and environmental conditions like pH and temperature (A)</p> Signup and view all the answers

The viral capsid contributes to which aspect of the virus?

<p>The structural symmetry of the virus particle (D)</p> Signup and view all the answers

Which function of the viral capsid is critical for the virus to attach to a host cell?

<p>Facilitating receptor attachment through specific proteins on the capsid (C)</p> Signup and view all the answers

What does the viral capsid facilitate during the packaging process?

<p>Recognition and packaging of the viral genome (A)</p> Signup and view all the answers

Why are antigenic sites on the viral capsid important?

<p>They determine the antigenicity of the virus (B)</p> Signup and view all the answers

Which of the following is NOT a function of the viral capsid?

<p>Synthesizing viral proteins in the host cell (C)</p> Signup and view all the answers

Which cellular membranes can contribute to the formation of a viral envelope?

<p>Cytoplasmic membrane, Golgi membrane, or nucleus membrane (A)</p> Signup and view all the answers

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

<p>Glycoproteins and matrix proteins (B)</p> Signup and view all the answers

What is the primary function of glycoproteins in the viral envelope?

<p>Perform receptor binding, hemagglutination, antigenicity, and membrane fusion (C)</p> Signup and view all the answers

What is the role of channel proteins in the viral envelope?

<p>Form a protein-lined channel that alters membrane permeability (A)</p> Signup and view all the answers

Which type of protein in the viral envelope plays a crucial role in virus assembly?

<p>Matrix protein (B)</p> Signup and view all the answers

What is the function of matrix proteins in the viral envelope?

<p>Stabilize the lipid envelope and link the nucleocapsid to the envelope (D)</p> Signup and view all the answers

How do glycoproteins in the viral envelope contribute to antigenicity?

<p>By being recognized as antigens by the host immune system (B)</p> Signup and view all the answers

What role does the matrix protein play at the plasma membrane during viral assembly

<p>It mediates the encapsulation of the RNA-nucleoprotein cores into the membrane envelope (D)</p> Signup and view all the answers

Which of the following is not a mechanism of genetic diversity of viruses?

<p>Conjugation (D)</p> Signup and view all the answers

What condition is required to maintain the lipid bilayer in the envelope of a virus?

<p>Aqueous or moist environments (B)</p> Signup and view all the answers

Why are enveloped viruses more susceptible to sterilization compared to non-enveloped viruses?

<p>Their lipid bilayer can be dissolved by lipid solvents (A)</p> Signup and view all the answers

Which of the following substances can inactivate enveloped viruses by dissolving their lipid membrane?

<p>Ether and chloroform (A)</p> Signup and view all the answers

What environmental factors can inactivate the lipid bilayer of enveloped viruses?

<p>Desiccation, heat and alteration of pH</p> Signup and view all the answers

What is antigenic drift in viruses?

<p>Mutation that results in minor changes to the virus (A)</p> Signup and view all the answers

What is one possible outcome of antigenic drift in viruses?

<p>Viruses become resistant to antiviral drugs (B)</p> Signup and view all the answers

What is antigenic shift in viruses?

<p>Reassortment of genetic material in viruses with segmented genomes (C)</p> Signup and view all the answers

What are the two mechanisms of antigenic shift?

<p>Recombination and reassortment</p> Signup and view all the answers

What is the primary difference between recombination and reassortment in antigenic shift?

<p>Recombination occurs within a single virus, while reassortment involves two viruses with segmented genomes (B)</p> Signup and view all the answers

Which mechanism of genetic diversity is most important in viruses with segmented genomes?

<p>Reassortment (C)</p> Signup and view all the answers

Which viral enzyme enables a retrovirus to integrate its genetic material into the host's DNA?

<p>Retroviral integrase (B)</p> Signup and view all the answers

What is the function of reverse transcriptase in viral infection?

<p>It generates complementary DNA (cDNA) from an RNA template (B)</p> Signup and view all the answers

What role does nucleic acid polymerase play in viruses?

<p>Facilitates viral genome replication (C)</p> Signup and view all the answers

Which type of viral protein is NOT typically present in extracellular virions?

<p>Nonstructural proteins (C)</p> Signup and view all the answers

Which enzyme is critical for retroviruses like HIV to successfully incorporate their genetic material into the host's DNA?

<p>Retroviral integrase (B)</p> Signup and view all the answers

Aberrations in Virus morphology

<p>Incomplete virion = Virion without nucleic acid (empty capsid) Pseudovirion = Contains host nucleic acid instead of viral nucleic acid, therefore fake genome Defective virion = Virus can’t replicate because it lacks a copy of viral genes Psuedotypes = Related viruses infect the same cell and switch genomes</p> Signup and view all the answers

Flashcards

Smallest known virus

Porcine circovirus type 1 is considered the smallest known virus.

Largest known virus

The largest virus in size is the Pox virus.

Pleomorphism

Pleomorphism in virology refers to the ability of a virus to change its shape or size.

Filament-shaped virus

The Ebola virus has a filament-shaped structure.

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Bullet-shaped virus

The rabies virus has a characteristic bullet-shaped structure.

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Rod-shaped virus

Tobacco mosaic virus is rod-shaped.

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Tadpole-shaped virus

Bacteriophages have a tadpole-shaped structure.

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Brick-shaped virus

The poxvirus is described as brick-shaped.

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Methods for determining virus morphology

Electron microscopy, cryo-EM, X-ray crystallography, and nuclear magnetic resonance (NMR) are common methods used to determine the morphology of viruses.

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Capsid

The protein coat that encases a virus's nucleic acid is called the capsid.

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Capsomeres

Capsomeres are the basic subunits that make up a virus's capsid.

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Layers of a virus

The layers of a virus can be compared to a winter jacket. The envelope is the outermost layer, the capsid is the middle layer, and the nucleic acid is the innermost layer.

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Double-layered capsid

Reoviruses are unique for having a double-layered capsid.

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Technique NOT used for virus morphology

Gram staining is not a commonly used technique to determine virus morphology.

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Function of the capsid

The main function of the capsid in a virus is to encapsulate and protect the viral nucleic acid/genome.

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Nucleocapsid

The term nucleocapsid refers to the combination of the capsid and the virus's nucleic acid (DNA or RNA).

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Acquiring an envelope

Viruses acquire an envelope by budding through the host cell membrane.

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Helical capsid symmetry

All animal viruses with helical nucleocapsids have helical capsid symmetry.

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Helical nucleocapsids in plants

Helical nucleocapsids in plant viruses are always naked, meaning they don't have a lipid envelope.

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Types of capsomeres

Icosahedral capsid symmetry has two types of capsomeres: pentagonal capsomeres (pentons) and hexagonal capsomeres (hexons).

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Number of pentons

There are always 12 pentagonal capsomeres (pentons) present in an icosahedral capsid.

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T-number calculation

The triangulation number (T-number) of an icosahedral capsid is calculated using the formula: T = h^2 + h x k + k^2.

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T-number of simplest virus

The simplest icosahedral virus, such as parvovirus, has a T-number of 1.

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T-number in Reoviridae

In Reoviridae, the inner capsid layer has a T-number of 2, while the outer capsid layer has a T-number of 13.

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Complex capsid symmetry

Complex capsid symmetry in viruses characterizes viruses with several parts, each with distinct shapes and symmetries.

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Example of complex symmetry

Poxvirus is an example of complex symmetry.

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Complex symmetry in bacteriophages

Viruses with complicated structures and exhibiting complex symmetry are typically bacteriophages.

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Protection by the capsid

The viral capsid protects the nucleic acid of a virus by acting as a barrier against enzymes, chemicals, and environmental conditions such as pH and temperature.

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Capsid and symmetry

The viral capsid contributes to the structural symmetry of the virus particle.

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Function of the capsid: Attachment

The capsid of a virus plays a crucial role in the attachment of the virus to a host cell by facilitating receptor attachment through specific proteins on the capsid surface.

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