Virus Classification: Methods and Characteristics
37 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Which of the listed characteristics is NOT a primary criterion used in the traditional hierarchical virus classification system?

  • Symmetry of the capsid.
  • Nature of the nucleic acid (DNA or RNA).
  • Specific host cell receptor interaction. (correct)
  • Presence or absence of an envelope.

    • In the Baltimore classification system, what serves as the central point for categorizing viruses?

  • Type of capsid symmetry.
  • Size of the viral genome.
  • Production of mRNA (+ sense RNA). (correct)
  • Presence of a viral envelope.

    • How does the genomic system classify viruses, especially in recent years?

  • According to the geographical location where the virus was first isolated.
  • Based on the host organism infected.
  • Primarily by the size and shape of the virion.
  • By analyzing the DNA or RNA sequence. (correct)

    • A newly discovered virus has been found to contain a single-stranded RNA genome and lacks an envelope. According to the traditional hierarchical classification, to what level can this virus be classified with the information provided?

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

    If a virus is classified as a positive-sense RNA virus by the Baltimore classification system, what key process must it perform upon entering a host cell?

    <p>It can directly use its RNA as mRNA for protein synthesis. (B)</p> Signup and view all the answers

    Which of the following characteristics is NOT a primary factor in determining the shape of a virus?

    <p>The specific sequence of the viral genome. (C)</p> Signup and view all the answers

    If a newly discovered virus has a capsid that appears to have flat sides and edges when viewed under an electron microscope, which shape would be most likely?

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

    A researcher identifies a virus that infects bacteria and has a distinct head-tail structure. The head appears icosahedral, and the tail is helical. How should this virus be classified based on its shape?

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

    Which of the following viruses is known to have the largest diameter?

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

    A newly discovered virus infects only specific strains of a bacterial species. This is an example of:

    <p>Host range specificity (A)</p> Signup and view all the answers

    Which of the following factors is MOST crucial for a virus to successfully infect a host cell?

    <p>Complementary fit between viral surface proteins and host cell receptors (B)</p> Signup and view all the answers

    What is the function of the protein subunits that surround the RNA molecules in a non-enveloped helical virus such as the Tobacco Mosaic Virus (TMV)?

    <p>To provide structural support and protection for the viral genome (B)</p> Signup and view all the answers

    A virus is found to exclusively target and infect nerve cells in humans. What property of this virus allows it to exhibit such specific targeting?

    <p>The complementary interaction between its surface proteins and specific receptors on nerve cells (C)</p> Signup and view all the answers

    Which factor primarily dictates a virus's capacity to infect a specific host cell?

    <p>The presence of specific receptors on the host cell surface that match viral attachment structures. (D)</p> Signup and view all the answers

    A virus with a narrow host range is MOST likely to infect:

    <p>a single tissue within a single species. (C)</p> Signup and view all the answers

    Before 1966, how were viruses commonly named?

    <p>Based on associated diseases, the type of disease they cause, or the sites in the body affected. (A)</p> Signup and view all the answers

    The ICTV's (International Committee on Taxonomy of Viruses) classification system is MOST important from which taxonomic level?

    <p>Family down to species. (C)</p> Signup and view all the answers

    What MUST occur before any translation can occur for a virus with a negative-sense (-) RNA genome?

    <p>The negative-sense RNA must be transcribed into a positive-sense (+) RNA. (D)</p> Signup and view all the answers

    Which characteristic is NOT a primary factor used in the classification of viruses?

    <p>The method of viral transmission between hosts. (A)</p> Signup and view all the answers

    Which of the following viruses is MOST likely to exhibit a broad host range?

    <p>A virus capable of transmitting from animals to humans but not between humans. (A)</p> Signup and view all the answers

    What is the correct suffix for viral families in the hierarchical virus classification?

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

    Which characteristic of viral capsomeres is most important for viral classification and identification?

    <p>The number of proteins and arrangement. (A)</p> Signup and view all the answers

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

    <p>Enveloped viruses have a bilayer membrane outside their capsid, whereas naked viruses do not. (D)</p> Signup and view all the answers

    Which component of an enveloped virus is typically derived from the host cell during the budding process?

    <p>The lipid membrane. (D)</p> Signup and view all the answers

    What is the term for a complete virus particle, including its envelope (if present)?

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

    What advantage do envelope proteins provide to viruses regarding the host's immune system?

    <p>Envelope proteins allow viruses to be hidden from attack by the host’s immune system. (B)</p> Signup and view all the answers

    Which environmental condition is least likely to damage enveloped viruses?

    <p>Stable pH levels around 7. (D)</p> Signup and view all the answers

    Viruses are considered metabolically inert outside of a host cell. What does this imply about their ability to function?

    <p>Viruses rely on the host cell's metabolic processes to reproduce. (C)</p> Signup and view all the answers

    What is the function of the glycoprotein spikes found on the surface of some viruses?

    <p>To enable the virus to attach to specific receptor sites on host cells. (B)</p> Signup and view all the answers

    Why is the property of hemagglutination useful in viral identification?

    <p>It demonstrates the virus's ability to cause red blood cells to clump together. (C)</p> Signup and view all the answers

    A newly discovered microorganism is non-cellular and contains DNA enclosed within a protein coat. It can only replicate inside a host cell. Which of the following is the most likely classification of this microorganism?

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

    Which of the characteristics listed is NOT a feature of viruses?

    <p>Possession of a nucleus (D)</p> Signup and view all the answers

    Outside of a host cell, a virus is metabolically inactive. How does the virus become active?

    <p>By invading a cell and directing the host machinery to synthesize new virions. (C)</p> Signup and view all the answers

    A researcher is studying a virus and finds that its genetic material is single-stranded RNA. Which of the following accurately describes the genetic composition of this virus?

    <p>It contains single-stranded RNA. (A)</p> Signup and view all the answers

    What is the primary function of the capsid?

    <p>To protect the viral nucleic acid. (A)</p> Signup and view all the answers

    Which of the following components are found in ALL viruses?

    <p>Nucleic acid and capsid (C)</p> Signup and view all the answers

    Why are viruses not classified into any of the established biological kingdoms (e.g., Animalia, Plantae, Fungi)?

    <p>Viruses do not possess the characteristics of living cells. (B)</p> Signup and view all the answers

    Flashcards

    Definition of Virus

    An infectious agent that can multiply only in living cells.

    Characteristics of Viruses

    Viruses are small, non-cellular, obligate intracellular parasites.

    Virus Components

    Viruses contain nucleic acid, capsid, and sometimes an envelope protein.

    Nucleic Acid in Viruses

    Viruses have either DNA or RNA as their genetic material.

    Signup and view all the flashcards

    Capsid Function

    The capsid is a protein coat that protects viral nucleic acid and gives shape.

    Signup and view all the flashcards

    Obligate Intracellular Parasite

    Viruses can only replicate inside the living cells of hosts.

    Signup and view all the flashcards

    Metabolic Activity of Viruses

    Viruses are metabolically inert outside of host cells.

    Signup and view all the flashcards

    Virus Replication Process

    Once inside a host cell, viruses direct its machinery to create new virus particles.

    Signup and view all the flashcards

    Capsomeres

    Protein subunits that compose the capsid of a virus.

    Signup and view all the flashcards

    Naked Virus

    A virus that consists only of capsid proteins without an envelope.

    Signup and view all the flashcards

    Enveloped Virus

    A virus that has a lipid bilayer membrane outside the capsid.

    Signup and view all the flashcards

    Virion

    A complete virus particle, including its capsid and envelope.

    Signup and view all the flashcards

    Nucleocapsid

    The combination of the viral genome and the capsid within a virion.

    Signup and view all the flashcards

    Spikes

    Glycoprotein projections from the viral envelope that help attach viruses to host cells.

    Signup and view all the flashcards

    Hemagglutination

    The clumping of red blood cells due to viral spikes binding to them.

    Signup and view all the flashcards

    Viral Size

    Viruses are measured in nanometers, often too small for light microscopes.

    Signup and view all the flashcards

    Smallest Virus

    The poliovirus measures 28 nm, similar in size to a ribosome.

    Signup and view all the flashcards

    Hierarchical Classification

    A system grouping viruses by phylum, class, order, family, genus, species, and strain.

    Signup and view all the flashcards

    Largest Virus

    The smallpox virus is the largest, measuring 200 nm in diameter.

    Signup and view all the flashcards

    Baltimore Classification System

    Classifies viruses based on their method of mRNA production, focusing on RNA types.

    Signup and view all the flashcards

    Helical Virus Shape

    Helical viruses have a spiral shape, often with RNA surrounded by protein subunits.

    Signup and view all the flashcards

    Viral Characteristics

    Classified based on nucleic acid type, capsid symmetry, envelope presence, and size.

    Signup and view all the flashcards

    Polyhedral Virus Shape

    Polyhedral viruses are shaped like geometric figures, with flat sides; e.g., adenovirus.

    Signup and view all the flashcards

    Genomic Classification

    Uses DNA/RNA sequences to organize viruses more accurately within families.

    Signup and view all the flashcards

    Complex Virus Structure

    Complex viruses, like bacteriophage, have an isocohedral head and helical tail.

    Signup and view all the flashcards

    mRNA Sense

    Viruses need to produce mRNA; (+) sense is the coding strand, whereas (-) sense is complementary.

    Signup and view all the flashcards

    Animal Viruses

    Animal viruses infect animals, including rabies, polio, and influenza.

    Signup and view all the flashcards

    Plant Viruses

    Plant viruses like TMV can infect plants, causing various diseases.

    Signup and view all the flashcards

    Host Range Specificity

    Viruses have a limited host range, attacking specific cells and tissues.

    Signup and view all the flashcards

    Broad host range

    Viruses that can infect multiple host species, such as swine flu and rabies.

    Signup and view all the flashcards

    Narrow host range

    Viruses that infect a single species or tissue type, such as adenovirus and HIV.

    Signup and view all the flashcards

    Virus specificity

    Determined by specific receptors on host cells and viral attachment structures.

    Signup and view all the flashcards

    Classification of viruses

    Based mainly on host type, nucleic acid type, polarity of RNA, and coat morphology.

    Signup and view all the flashcards

    Nucleic acid types

    Viruses can have dsDNA, dsRNA, ssDNA, or ssRNA as their genetic material.

    Signup and view all the flashcards

    Virus coat morphology

    Describes whether a virus has an envelope or not.

    Signup and view all the flashcards

    Hierarchical virus classification

    Classification important mainly from the family level onward, with families ending in 'viridae'.

    Signup and view all the flashcards

    Virus nomenclature history

    First 60 years were named based on diseases or the first locations discovered.

    Signup and view all the flashcards

    Study Notes

    Virus Introduction

    • Viruses are infectious agents.
    • They are very small, requiring a microscope to see.
    • They are not part of any kingdom (not plants, animals, fungi, protists, or bacteria).
    • They are obligate intracellular parasites; they can only replicate within a host cell, relying on host metabolic processes.
    • Viral diseases result from the interaction between the virus and host cell.

    Virus Characteristics

    • Viruses are too small to be seen with a light microscope.
    • They are non-cellular, lacking a nucleus, organelles, cytoplasm, or cell membrane.
    • Viruses are obligate intracellular parasites, meaning they multiply only inside living cells.
    • They cannot divide or live outside a host cell.
    • Outside a host cell (extracellular), viral metabolism is inactive, and biosynthetic functions are impossible.
    • Once inside a cell, they direct host machinery to produce new complete viral particles (virions), which complete the replication process.

    Virus Components

    • Viruses contain nucleic acid (either DNA or RNA).
    • The capsid, composed of capsomeres, provides a protective protein coat.
    • Some viruses have an envelope, a lipid-protein membrane outside the capsid.
      • The envelope is derived from host cell membranes, and the material may include carbohydrates
    • The nucleocapsid contains the viral genome along with the capsid.

    Viral Nucleic Acid

    • Viruses contain either DNA or RNA, but not both.
      • Nucleic acid can be double-stranded (DS), single-stranded (SS), linear, circular, or segmented.

    Viral Capsids

    • The capsid (or capsids) is the surrounding protein coat around the nucleic acid.
    • Determine the shape of the virus.
    • Contains protein subunits known as capsomeres.
    • The number and arrangement of capsomeres are important in classifying and identifying viruses.

    Viral Envelopes

    • Some viruses have a membrane called an envelope surrounding the capsid.
      • Consisting of lipids, proteins, and carbohydrates
    • Enveloped viruses are often derived from host cell membranes as they bud from or detach from the host cell.
    • Enveloped viruses can lose their envelope under harsh conditions (e.g., high temperature, freezing/thawing, certain chemicals).

    Viral Shapes and Sizes

    • Viruses exhibit various shapes (helical, polyhedral, complex).
    • Sizes fluctuate among different viruses.
      • Measured in nanometers (nm).
      • Poliovirus (28 nm) is the smallest virus shown; smallpox viruses are large (200 nm).

    Host Range and Specificity

    • Viruses have a limited host range, attacking only one or a few host types or cell types.
    • Viruses show specificity for cells/tissue—a complementary fit between external viral proteins and host cell surface proteins.
      • This specificity impacts the host cells infected.
    • Broad-range viruses can infect various host types (e.g., swine flu and rabies), while narrow-range viruses are limited to a single tissue type in a single species (e.g., HIV, phages on E. coli).

    Virus Classification

    • Viruses are classified based on their genetic material, morphology of their capsid, presence or absence of an envelope, and their host range.
    • The ICTV (International Committee on Taxonomy of Viruses) maintains a systematic system for classifying viruses.
    • Historically, method classification has been developed using the following:
      • type of disease caused;
      • site of the first virus isolation;
      • scientific discoverer of the virus;
      • perceived method of contraction

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Description

    Explore virus classification methods like hierarchical, Baltimore, and genomic systems. Learn about key characteristics and shapes used to classify viruses. This quiz assesses understanding of viral traits, including genome type and capsid structure.

    More Like This

    Use Quizgecko on...
    Browser
    Open
    Browser
    Browser