Week 6 & 7
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Questions and Answers

What role does Neuraminidase (NA) play in the influenza virus lifecycle?

  • It helps the virus penetrate mucus and aids in viral shedding. (correct)
  • It binds the virus to host cells.
  • It produces antibodies against the virus.
  • It combines the genomes of different viruses.

    • Antigenic shift occurs solely due to point mutations in the virus's genes.

    False

    What are the two proteins that are responsible for antigenic variation in the influenza virus?

    Hemagglutinin and Neuraminidase

    Antigenic _____ refers to the reassortment of viral genes from two different viruses that infect the same cell.

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

    Match the type of antigenic variation with its description:

    <p>Antigenic Drift = Results from point mutations in viral genes Antigenic Shift = Caused by reassortment of viral genes from different viruses</p> Signup and view all the answers

    What is a common characteristic of viruses?

    <p>They are acellular infectious agents.</p> Signup and view all the answers

    Viruses can enter host cells without binding to any receptors.

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

    Name one example of a virus.

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

    The viral replication cycle begins with __________ of the virus to the host cell.

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

    Match the following types of viral entry mechanisms with their descriptions:

    <p>Direct penetration = Only viral genome enters the host cell. Fusion = Viral envelope fuses with host membrane. Receptor mediated endocytosis = Entire virus enters via endocytosis. Exocytosis = Viruses leave using vesicles without killing the host.</p> Signup and view all the answers

    Which of the following statements about RNA viruses is true?

    <p>They adapt readily to environmental changes.</p> Signup and view all the answers

    During the uncoating phase of the viral replication cycle, the viral genome becomes exposed to the cytoplasm.

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

    What are the two spikes required for the infection process of the influenza virus?

    <p>Hemagglutinin and Neuraminidase</p> Signup and view all the answers

    What is the primary purpose of enrichment media?

    <p>To promote the growth of specific organisms present in small numbers</p> Signup and view all the answers

    All species within the Enterobacteriaceae family live in the gastrointestinal tract.

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

    Name one enzyme produced by bacteria that can digest lipids.

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

    The family Enterobacteriaceae belongs to the domain __________.

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

    Match the types of haemolytic bacteria with their descriptions:

    <p>Alpha haemolytic = Partial lysis of red blood cells Beta haemolytic = Complete lysis of red blood cells Gamma haemolytic = No lysis of red blood cells Non-haemolytic = Does not produce any effects on red blood cells</p> Signup and view all the answers

    Which of the following genera is NOT part of the Enterobacteriaceae family?

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

    MacConkey Agar is used exclusively for the growth of Gram-positive bacteria.

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

    What color do rapid fermenters produce on Eosin Methylene Blue Agar?

    <p>Green metallic colonies</p> Signup and view all the answers

    The genus _____ is known for species like E. coli and E. albertii.

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

    Match the following Enterobacteriaceae genera with their species:

    <p>Salmonella = enterica Klebsiella = pneumoniae Shigella = flexneri Yersinia = pestis</p> Signup and view all the answers

    What color do lactose fermenters produce on MacConkey agar?

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

    Mannitol Salt Agar is selective for gram-negative bacteria.

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

    What is the purpose of adding blood to Chocolate Agar?

    <p>To provide nutrients and allow differentiation of bacteria based on their hemolytic properties.</p> Signup and view all the answers

    Blood Agar can differentiate between ___________ bacteria.

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

    Match the following enrichment media with their characteristics:

    <p>Tryptic Soy Agar = General purpose non-selective media Blood Agar = Contains 5% bovine or sheep blood Chocolate Agar = Heated blood in tryptic soy agar Broth = Liquid media for growing bacteria</p> Signup and view all the answers

    Which type of bacteria can produce black colonies on Hektoen Enteric Agar?

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

    Alpha hemolytic bacteria completely lyse red blood cells.

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

    What distinguishes pathogenic Staphylococci from non-pathogenic ones on Mannitol Salt Agar?

    <p>Pathogenic Staphylococci ferment mannitol, while non-pathogenic do not.</p> Signup and view all the answers

    Study Notes

    University of Doha for Science & Technology

    • University of Doha for Science & Technology (UDST)
    • College of General Education

    Viruses

    • Viruses are acellular infectious agents
    • They cannot self-replicate
    • They must infect a cell to make copies of themselves
    • Examples: Influenza, HIV, Ebola

    Viral Structure

    • Common Features:
      • RNA or DNA genome
      • Capsid of proteins
      • Envelope lipid bi-layer
      • Surface receptors - Spikes of protein or glycoprotein

    Viral Replication Cycle

    • Replicative cycle depends on the virus's genome
    • ssRNA viruses have a different replicative cycle than dsDNA viruses
    • The image shows a general mechanism
      • Attachment: Viral proteins on the envelope or capsid bind to host cell receptors
      • Penetration: Entry is through one of three mechanisms: direct penetration, fusion, or receptor-mediated endocytosis
      • Uncoating: The virus removes its capsid; the genome is exposed to the cytoplasm
      • Transport to Nucleus: Viral genome enters the nucleus
      • Synthesis (Transcription & Translation): Viral genome reproduction (transcription in nucleus) and viral protein synthesis (translation in cytoplasm)
      • Assembly: New virus components are assembled to create new viruses
      • Release: The virus is released from the host cell via apoptosis, budding, or exocytosis

    Viral Shedding

    • Three mechanisms:
      • Apoptosis: Host cell lyses and releases mature viral particles.
      • Budding: Virus exits through nuclear or plasma membrane, creating an envelope.
      • Exocytosis: Virus leaves the host cell using vesicles.

    Influenza Virus

    • Enveloped RNA virus
    • RNA viruses make more mistakes than DNA viruses
    • They don't have self-regulation
    • They adapt readily to environmental changes due to high mutation rates
    • Envelope is covered with 2 proteins (antigens) required for infection: Hemagglutinin (H) spike and Neuraminidase (N) spike

    Hemagglutinin (HA)

    • Glycoprotein on the surface of influenza virus
    • Binds to sialic acid receptors on host cells
    • Helps the virus enter cells in upper respiratory tracts
    • The structure of HA is affected by mutations, responsible for the emergence of new strains of influenza.

    Neuraminidase (NA)

    • Enzyme that helps the virus penetrate mucus
    • Aids in viral shedding (budding) by cutting sialic acid from host glycoproteins.

    Antigenic Variation

    • Occurs in two ways for influenza viruses:
      • Antigenic drift: Point mutations in genes coding for Hemagglutinin (HA) and Neuraminidase (NA)
      • Antigenic shift: Reassortment of viral genes resulting in the emergence of new virus strains

    Antigenic Shift

    • Results from gene re-assortment of two different viruses
    • Viruses exchange a large part of their genome
    • The emerging virus is antigenically different from the parent viruses
    • Antibodies from parent viruses are ineffective against the new virus
    • Examples include H1N1 (swine flu), H5N1 (bird flu)

    Swine Flu Viroid

    • Re-assortment of different genetic material within a cell results in the creation of a new strain
    • Genetic material from different sources re-combines

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    Description

    This quiz covers the basics of viruses, their structure, and the viral replication cycle. Explore key concepts including acellular infectious agents, genome types, and the steps involved in viral infection and replication. Perfect for students of General Education at UDST.

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