BIO 102: Characteristics of Viruses
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Questions and Answers

Which type of viruses require an RNA-dependent RNA polymerase for replication?

  • Double-stranded RNA viruses
  • Double-stranded DNA viruses
  • Single-stranded RNA negative-sense viruses (correct)
  • Single-stranded DNA viruses

    • Where do most double-stranded DNA viruses replicate within the host cell?

  • In the cytoplasm
  • In the mitochondria
  • In the nucleus (correct)
  • In the endoplasmic reticulum

    • Which statement accurately describes positive-sense RNA viruses?

  • They replicate exclusively in the nucleus.
  • Their genome can be directly translated into mRNA. (correct)
  • They convert their RNA genome into DNA for integration.
  • They require reverse transcription before replication.

    • What is the term for a phage that integrates its genetic material into the host's chromosome and remains in a dormant state?

    <p>Prophage</p> Signup and view all the answers

    Which of the following viruses utilizes reverse transcriptase during its replication cycle?

    <p>HIV</p> Signup and view all the answers

    What characteristic distinguishes retroviruses from other RNA viruses?

    <p>They integrate their genome into the host DNA.</p> Signup and view all the answers

    Which of the following viruses is specifically associated with producing persistent infections by integrating their nucleic acid into the host cell chromosome?

    <p>Herpesvirus</p> Signup and view all the answers

    In what form does a temperate phage exist when it carries its genetic material in a stable and non-infectious manner?

    <p>Prophage</p> Signup and view all the answers

    Which type of virus must first convert its genome into double-stranded DNA before replication and transcription?

    <p>Single-stranded DNA viruses</p> Signup and view all the answers

    What typically triggers the activation of latent infections in viruses?

    <p>Compromised host immunity</p> Signup and view all the answers

    Rotaviruses are classified as which type of virus based on their genome structure?

    <p>Double-stranded RNA</p> Signup and view all the answers

    Which mechanism do some DNA viruses, like Poxviruses, utilize for replication?

    <p>They utilize their own replication machinery in the cytoplasm.</p> Signup and view all the answers

    Which component of a virion is responsible for protecting the viral genome and facilitating attachment to host cell receptors?

    <p>Capsid</p> Signup and view all the answers

    How is the transmission of the herpes virus illustrated in human populations?

    <p>Carried over generations</p> Signup and view all the answers

    What is the primary characteristic of latent infections caused by viruses such as mumps and measles?

    <p>They produce infected daughter host cells.</p> Signup and view all the answers

    Viruses are classified based on several criteria. Which of the following is NOT a criterion used for their classification?

    <p>Host immune response</p> Signup and view all the answers

    Which type of bacteria obtains energy from the oxidation of inorganic compounds and carbon from carbon dioxide?

    <p>Chemoautotroph</p> Signup and view all the answers

    What is the primary energy yield of aerobic respiration per glucose molecule?

    <p>38 ATP</p> Signup and view all the answers

    Which method involves using a series of steps including crystal violet staining and safranin counterstaining?

    <p>Gram Staining</p> Signup and view all the answers

    What do photoheterotrophs use as their carbon source?

    <p>Organic compounds</p> Signup and view all the answers

    Which type of respiration occurs in the absence of oxygen and produces only 2 ATP per glucose?

    <p>Fermentation</p> Signup and view all the answers

    Which type of bacterial identification method uses solid media for bacterial growth?

    <p>Culture Techniques</p> Signup and view all the answers

    What distinguishes Gram-positive bacteria from Gram-negative bacteria during staining?

    <p>Cell wall thickness</p> Signup and view all the answers

    What is a primary characteristic of chemoheterotrophs?

    <p>Require organic compounds for carbon and energy</p> Signup and view all the answers

    Which characteristic is unique to the classification of Chytridiomycota among fungal groups?

    <p>They possess flagellated spores known as zoospores.</p> Signup and view all the answers

    What is the role of well-known stains like lactophenol cotton blue in fungal identification?

    <p>To depict fungal structures under a microscope.</p> Signup and view all the answers

    Which of the following methods is NOT typically used in fungal identification?

    <p>Genetic engineering techniques.</p> Signup and view all the answers

    What is the primary feature that distinguishes Ascomycota from Zygomycota?

    <p>Production of sexual spores within asci.</p> Signup and view all the answers

    Which type of growth media is commonly used for culturing fungi?

    <p>Potato dextrose agar.</p> Signup and view all the answers

    Which technique is used to analyze genetic variation in fungi by examining DNA fragment patterns?

    <p>Restriction Fragment Length Polymorphism (RFLP).</p> Signup and view all the answers

    Which metabolic profiling technique helps in distinguishing different fungal species?

    <p>Identifying carbon and nitrogen source utilization.</p> Signup and view all the answers

    Which fungal group includes organisms known to be major saprophytes or parasites and produce a distinct type of spore?

    <p>Chytridiomycota.</p> Signup and view all the answers

    What is the primary metabolic characteristic of viruses?

    <p>They rely on host metabolism for replication.</p> Signup and view all the answers

    In which phase of viral replication can no virus particles be detected?

    <p>Eclipse phase</p> Signup and view all the answers

    How do viruses typically gain entry into host cells?

    <p>Through the absorption to specific receptor sites.</p> Signup and view all the answers

    Which mechanism is described as less destructive for the host cell during the release of new viral particles?

    <p>Budding at the cell membrane surface.</p> Signup and view all the answers

    What type of nucleic acid can be found in viruses?

    <p>Either single or double-stranded DNA or RNA</p> Signup and view all the answers

    What is the typical replication time for a prokaryotic virus such as a bacteriophage?

    <p>Minutes</p> Signup and view all the answers

    What happens to a virus's infective nature outside its host?

    <p>Viruses remain inert and unable to move.</p> Signup and view all the answers

    What is the significance of the specific receptor sites found on a virus's capsid or envelope?

    <p>They allow the virus to attach and enter the appropriate host cells.</p> Signup and view all the answers

    Study Notes

    Basic Characteristics of Viruses

    • Viruses can infect both eukaryotic and prokaryotic organisms.
    • They are obligate parasites, lacking metabolic capacity and relying entirely on host metabolism for replication.
    • Composed of nucleic acid (DNA or RNA) encased in a protein coat (capsid).
    • Viral nucleic acids can be single-stranded or double-stranded, DNA or RNA.
    • Virus replication involves five steps: adsorption, penetration, replication, maturation, and release.

    Infection Mechanisms

    • Viruses use specific receptors on their capsids or envelopes to enter target cells.
    • After penetrating the host cell, viruses enter an eclipse phase where no viral particles are detectable.
    • New viral components are produced and released through cell lysis or budding from the membrane, with budding being less harmful to the host.

    Infective Nature of Viruses

    • Viruses are inert outside host organisms and require vehicles for transport (air/water).
    • Infection can be asymptomatic or lead to acute, chronic, or latent infections.
    • In bacteria, some viruses (phages) can remain dormant (lysogeny) within the host cell's chromosome as a prophage, which can reactivate under certain conditions.

    Structure and Function of Viruses

    • Virions consist of nucleic acid (genetic material), a protein coat (capsid), and, in enveloped viruses, an outer lipid bilayer with glycoproteins.
    • Capsomeres form the capsid; its structure is essential for protection and attachment to host cells.

    Classification of Viruses

    • Classification is based on size, shape, genome structure, and chemical composition.
    • DNA viruses include:
      • Single-stranded DNA (ssDNA) such as Parvoviruses.
      • Double-stranded DNA (dsDNA) such as Herpesviruses.
    • RNA viruses include:
      • Positive-sense RNA (+ssRNA), which can directly serve as mRNA (e.g., Poliovirus).
      • Negative-sense RNA (-ssRNA), requiring synthesis of a complementary RNA strand (e.g., Influenza virus).
      • Double-stranded RNA (dsRNA) includes Rotaviruses.
      • Retroviruses (e.g., HIV) convert RNA into DNA via reverse transcriptase.

    Replication Strategies

    • DNA viruses replicate in the nucleus using host enzymes, while some (like Poxviruses) replicate in the cytoplasm.
    • RNA viruses replicate in the cytoplasm, with positive-sense RNA being translatable to proteins.
    • Retroviruses integrate their genetic material into the host cell's DNA for persistence.

    Bacterial Metabolism

    • Bacteria can be chemoheterotrophs, chemoautotrophs, photoautotrophs, or photoheterotrophs based on energy and carbon sources.
    • Respiration includes:
      • Aerobic respiration (producing 38 ATP/glucose),
      • Anaerobic respiration (using alternative electron acceptors),
      • Fermentation (yielding 2 ATP/glucose).

    Identification of Bacteria

    • Microscopy techniques like Gram staining distinguish between Gram-positive and Gram-negative bacteria based on cell wall structure.
    • Culture techniques, including the use of agar plates, help identify bacteria based on colony morphology and specific metabolic properties.

    Fungal Identification Techniques

    • Fungi are identified through morphological observation under microscopy, looking for structures like hyphae and spores.
    • Growth on specialized media aids identification, with temperature tolerance also being a potential identifying factor.
    • Biochemical tests assess enzyme activity and metabolic profiling, while molecular techniques like PCR and DNA sequencing provide precise classifications.

    Classification of Fungi

    • Fungi are categorized into major groups based on reproductive and genetic characteristics:
      • Chytridiomycota (primarily aquatic, flagellated spores).
      • Zygomycota (zygospores, coenocytic hyphae).
      • Ascomycota (sac fungi, ascospores).

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    Description

    This quiz covers the basic characteristics, identification, and classification of viruses, important entities in biology. Learn about their structure, metabolism, and their role as obligate parasites. This content is essential for understanding virology in general biology.

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