Introduction to Virology
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Questions and Answers

What are viruses classified as due to their inability to reproduce independently?

  • Prokaryotic organisms
  • Cellular entities
  • Eukaryotic organisms
  • Obligate intracellular parasites (correct)

Which component protects the viral genome from the environment?

  • Glycoproteins
  • Nucleocapsid
  • Envelope
  • Capsid (correct)

What type of genetic material can viruses contain?

  • Either DNA or RNA, but never both (correct)
  • Only DNA
  • Only RNA
  • Both DNA and RNA

What is a defining feature of helical viruses?

<p>Capsid proteins arranged in a helical pattern (B)</p> Signup and view all the answers

What happens during the lytic cycle of viral replication?

<p>New virus particles cause the host cell to lyse (A)</p> Signup and view all the answers

What is the function of glycoproteins in enveloped viruses?

<p>Facilitating attachment to host cells (C)</p> Signup and view all the answers

What distinguishes segmented genomes during genetic exchange?

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

Which type of viruses specifically infect bacteria?

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

What is the primary characteristic of naked viruses?

<p>They lack a lipid bilayer envelope (A)</p> Signup and view all the answers

What method do enveloped viruses typically use to enter host cells?

<p>Direct fusion with the host membrane (A)</p> Signup and view all the answers

What defines whether a virus is classified as enveloped or naked?

<p>The presence or absence of a lipid membrane. (B)</p> Signup and view all the answers

Which of the following describes the lytic cycle of a virus?

<p>The virus causes the host cell to lyse after replication. (A)</p> Signup and view all the answers

What occurs during reassortment in segmented viruses?

<p>Exchange of genetic material between segmented viruses. (C)</p> Signup and view all the answers

What role do capsids play in viral structure?

<p>They enclose and protect the viral genome. (C)</p> Signup and view all the answers

Which of the following is NOT a characteristic used to classify viruses?

<p>Color of the virus. (B)</p> Signup and view all the answers

What is the relationship between Hepatitis B and Hepatitis D?

<p>Hepatitis B provides a capsid necessary for Hepatitis D's survival. (B)</p> Signup and view all the answers

How do enveloped viruses typically enter host cells?

<p>Via direct fusion with the host membrane. (A)</p> Signup and view all the answers

Which method allows one functional virus to provide a component to a defective virus?

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

What is a significant outcome of the lysogenic cycle?

<p>Dormancy of the viral genetic material. (B)</p> Signup and view all the answers

Which viral family is responsible for causing influenza?

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

What characterizes phenotypic mixing in viruses?

<p>Exchange of protein capsids between two functional viruses. (A)</p> Signup and view all the answers

What characterizes single-stranded RNA viruses?

<p>Their single linear or circular RNA content. (B)</p> Signup and view all the answers

Which of the following describes a key feature of viruses?

<p>They are classified by their genome and structure. (D)</p> Signup and view all the answers

What process allows genetic material exchange between two viruses?

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

What is a common method used by both naked and enveloped viruses to enter host cells?

<p>Receptor-mediated endocytosis. (B)</p> Signup and view all the answers

What process do viruses potentially utilize to undergo genetic exchange?

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

Which component of the virus binds to host cell receptors?

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

What is a characteristic feature of enveloped viruses like influenza?

<p>They have a lipid membrane. (A)</p> Signup and view all the answers

Which of the following is NOT a method viruses use to exchange genetic material?

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

What does the lysogenic cycle involve in viral replication?

<p>Integration of viral DNA into the host genome. (B)</p> Signup and view all the answers

Flashcards

Obligate intracellular parasite

A virus that needs a host cell to replicate and produce proteins.

Viral Capsid

A protein coat surrounding the viral genome.

Nucleocapsid

The capsid and viral genetic material together.

Viral Envelope

Lipid membrane surrounding some viruses.

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Lytic Cycle

Viral replication that destroys the host cell.

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Lysogenic Cycle

Viral replication that integrates viral DNA into host genome.

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Viral Recombination

Genetic exchange between two viruses in same host.

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Viral Reassortment

Genetic mixing of segmented viral genomes.

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Icosahedral Capsid

20-sided protein structure that forms the viral capsid.

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Bacteriophage

Virus that infects bacteria.

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What makes a virus non-living?

Viruses lack the machinery for independent replication and must rely on a host cell for their life cycle.

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What is the role of viral glycoproteins?

Glycoproteins on a virus's envelope bind to specific receptors on the host cell's surface, initiating infection.

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Helical Capsid

A viral capsid structure with proteins arranged in a spiral or helical shape.

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What is a bacteriophage?

A virus that specifically targets and infects bacteria.

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What is the difference between a naked and an enveloped virus?

A naked virus lacks a lipid membrane envelope, while an enveloped virus has a lipid membrane surrounding its capsid.

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What is a lysogenic cycle?

A viral replication cycle where the viral genome integrates into the host's genome, remaining dormant until triggered.

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Tail Injection

Bacteriophages use a tail-like structure to inject their genetic material into the host cell.

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How does receptor-mediated endocytosis work?

The host cell mistakes the virus for a necessary substance and engulfs it by endocytosis, allowing the virus to enter the cell.

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What is viral recombination?

Exchange of genetic material between two different viruses that infect the same host cell.

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Influenza Pandemics

Pandemics caused by reassortment of influenza virus genes, resulting in a new strain with increased transmissibility or virulence.

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Hepatitis D

A defective RNA virus that requires Hepatitis B to survive and replicate, relying on Hepatitis B's capsid.

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Viral Complementation

One functional virus provides a missing component (like a capsid) to a defective virus, allowing the defective virus to replicate.

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Phenotypic Mixing

Exchange of protein capsids between two functional viruses, resulting in a virus with a coat from one virus and the genetic material from another.

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What makes Hepatitis D defective?

Hepatitis D is a defective RNA virus that lacks its own capsid and relies on Hepatitis B to provide it.

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What are the effects of viral reassortment?

Reassortment can create new virus strains with altered properties, including increased transmissibility or virulence, potentially leading to pandemics.

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What do viruses need to replicate?

Viruses require a host cell's machinery to replicate. They need components like capsids, enzymes, and ribosomes.

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How are viruses classified?

Viruses are classified based on their genome type (DNA or RNA), structure (envelope, capsid), host range, and method of replication.

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What are the types of viral replication cycles?

The two major types are lytic and lysogenic. Lytic cycles destroy the host cell, while lysogenic cycles integrate viral DNA into the host's genome.

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Study Notes

Introduction to Virology

  • Viruses are acellular entities, meaning they are not cells and cannot reproduce independently.
  • They are obligate intracellular parasites, requiring a host cell to replicate and produce proteins.
  • Viruses are essentially packages of nucleic acids, either DNA or RNA, but never both.

Viral Structure

  • Capsid: A protein coat surrounding the genome, protecting it from the environment.
  • Nucleocapsid: The capsid and the genetic material within.
  • Envelope: Some viruses have a lipid membrane surrounding the capsid, containing glycoproteins for attachment to host cells.

Viral Classification

  • Genome Composition:
    • Type of nucleic acid: DNA or RNA viruses.
    • Number of strands: Single-stranded or double-stranded DNA/RNA.
    • Genome geometry: Linear or circular.
  • Capsid Structure:
    • Helical: Capsid proteins arranged in a helical pattern, like a tube.
    • Icosahedral: Proteins arranged in equilateral triangles, forming a 20-sided structure.
    • Complex: A combination of helical and icosahedral structures.
  • Presence of Envelope:
    • Naked: No envelope present
    • Enveloped: Surrounded by a lipid bilayer envelope.
  • Host Type:
    • Bacteriophages: Viruses that infect bacteria.
  • Method of Action:
    • Tail-like: Used by bacteriophages to inject their genetic material into the host.
    • Direct Fusion: Enveloped viruses fuse with the host cell membrane.
    • Receptor-mediated endocytosis: Viruses, both naked and enveloped, enter the cell through receptors.

Viral Replication

  • Lytic Cycle: The virus uses the host cell's machinery to replicate and produce new virus particles, causing the cell to lyse (rupture).
  • Lysogenic Cycle: Viral genetic material integrates into the host cell's genome (provirus), remaining dormant. The host cell replicates, carrying the viral genetic material. This cycle can trigger the lytic cycle, causing the release of new viruses.

Viral Genetic Exchange

  • Recombination: Two viruses enter a host cell, their genetic material mixes, and they exchange DNA/RNA segments.
  • Reassortment: Occurs with segmented genomes (e.g., influenza viruses). Genetic material is exchanged between different segments of the virus.
  • Complementation: One functional virus provides a missing component (e.g., capsid) to a defective virus.
  • Phenotypic Mixing: Two functional viruses exchange capsids; both viruses remain functional.

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Description

This quiz explores the fundamental concepts of virology, including the nature and structure of viruses. Understand the classification based on genome composition and capsid structure. Test your knowledge on how viruses operate as obligate intracellular parasites and the roles of different viral components.

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