Virology and Virus Characteristics Quiz
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Questions and Answers

What is a characteristic of viroids?

  • They are made of protein.
  • They consist of short strands of infectious RNA. (correct)
  • They are larger than viruses.
  • They require a helper virus for replication.

    • Prions are well understood and their structure is clearly defined.

    False

    What type of vaccine is made from live, attenuated microorganisms?

    Attenuated vaccine

    A vaccine is a biological preparation that improves ____ to a particular disease.

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

    Match the following diseases with their associated prion disorders:

    <p>Scapie = A degenerative disease in sheep Bovine spongiform encephalopathy = Mad cow disease Kuru = A disease transmitted through cannibalism Creutzfeldt-Jakob disease = A fatal human neurodegenerative disorder</p> Signup and view all the answers

    What are the two types of capsomers found in virus capsids?

    <p>Pentamers and Hexamers</p> Signup and view all the answers

    Poxviruses are the smallest of the animal viruses.

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

    What is the structure that contains the double-stranded DNA in poxviruses?

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

    Many viruses are bounded by an outer membranous layer called the ______.

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

    Match the following virus characteristics with their descriptions:

    <p>Envelope = Membranous layer surrounding the nucleocapsid Pleomorphic = Variable shape of enveloped viruses Ether sensitive = Disrupted envelopes due to solvents Spikes = Surface projections for host attachment</p> Signup and view all the answers

    Which of the following statements about enveloped viruses is true?

    <p>Enveloped viruses can vary in shape and are often pleomorphic.</p> Signup and view all the answers

    The viral structure consisting of a head resembling an icosahedron and a helical tail exhibits ______ symmetry.

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

    What type of nucleic acid do most RNA viruses contain?

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

    All viruses are made up of double-stranded DNA.

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

    What is the classification of SARS-CoV-2?

    <p>Beta-coronavirus</p> Signup and view all the answers

    SARS-CoV-2 contains approximately _____ nucleotides in its RNA genome.

    <p>29,903</p> Signup and view all the answers

    Which of the following is TRUE about viral enzymes?

    <p>They are primarily found within the viral capsid.</p> Signup and view all the answers

    Match the viral genome types with their description:

    <p>Single-stranded DNA = Common in plant viruses Double-stranded RNA = Usually segmented Single-stranded RNA = Can be plus or minus Double-stranded DNA = Typically stable and less mutagenic</p> Signup and view all the answers

    All segments of segmented RNA genomes are contained within separate capsids.

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

    What is the diameter of the SARS-CoV-2 virus?

    <p>~120 nm</p> Signup and view all the answers

    RNA viruses may have a genome that can be _____ or _____ when compared with mRNA.

    <p>plus, minus</p> Signup and view all the answers

    Which of the following is NOT one of the five steps of virus reproduction?

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

    Viruses can reproduce independently of living cells.

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

    What is the process where viral genes are transcribed and translated called?

    <p>Synthesis of viral nucleic acid and proteins</p> Signup and view all the answers

    Viruses are cultivated using tissue cultures, embryonated eggs, and __________.

    <p>bacterial cultures</p> Signup and view all the answers

    Which type of nucleic acids can animal viruses have?

    <p>Both single-stranded and double-stranded</p> Signup and view all the answers

    Match the following steps of virus reproduction with their descriptions:

    <p>Step 1 = Attachment of the virion to a host cell Step 2 = Penetration of viral nucleic acid into the host Step 3 = Synthesis of viral nucleic acid and proteins Step 4 = Self-assembly and packaging of new virions Step 5 = Release of mature virions</p> Signup and view all the answers

    Carcinogenesis is a simple process that involves few factors.

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

    What is the area called where a bacterial lawn is cleared due to phage infection?

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

    Name a cancer associated with Hepatitis B virus.

    <p>Hepatocellular carcinoma</p> Signup and view all the answers

    Fertilized chicken eggs can be used for the cultivation of viruses.

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

    The Epstein-Barr virus (EBV) is linked to _________ lymphoma.

    <p>Burkitt’s</p> Signup and view all the answers

    What effect do some animal viruses have on tissue and cells?

    <p>Cytopathic effects</p> Signup and view all the answers

    Match the following viruses with their associated cancers:

    <p>Hepatitis C virus = Cirrhosis of the liver Human papillomavirus = Cervical cancer Epstein-Barr virus = Burkitt’s lymphoma HIV = Karosi’s sarcoma</p> Signup and view all the answers

    The technique used to count virus particles directly is ______________.

    <p>electron microscopy</p> Signup and view all the answers

    Match the type of viral quantification method with its description:

    <p>Hemagglutination assay = Indirect counting through agglutination Plaque assay = Counting clear zones in a bacterial lawn Electron microscopy = Direct visualization of virus particles Cytopathic effects = Infection often characterized by cell damage</p> Signup and view all the answers

    How do plant viruses usually enter their host?

    <p>Via mechanical damage</p> Signup and view all the answers

    Most plant viruses have a DNA genome.

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

    What is a common mechanism through which plant viruses are transmitted?

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

    HTLV-1 is associated with _________ T-cell leukemia.

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

    What is one of the ways that viruses can induce cancer?

    <p>By bringing a cancer-causing agent into a cell</p> Signup and view all the answers

    Study Notes

    Virus Properties and Structure

    • Viruses are simple, acellular entities.
    • They reproduce only within living cells.
    • They are obligate intracellular parasites.
    • Viruses exist in two phases: extracellular and intracellular.
    • Virions (extracellular phase) have few, if any enzymes, cannot reproduce independently of living cells.
    • In the intracellular phase, viruses exist primarily as replicating nucleic acid.
    • Viruses induce host metabolism to synthesize virion components.
    • All virions have a nucleocapsid.
    • The nucleocapsid is composed of nucleic acid (DNA or RNA, but not both) enclosed in a protein coat.
    • The protein capsid is made of protomers.
    • Viral capsids can be helical, icosahedral, or complex.
    • Enveloped viruses have an envelope, whereas naked viruses do not.

    Early Development of Virology

    • Europeans were first protected from a viral disease when Edward Jenner developed a smallpox vaccine in 1798.
    • Viruses were discovered after the development of the Chamberland-Pasteur filter.
    • The filter removed bacteria visible in microscopes from any liquid sample.
    • This demonstrated the existence of viruses as separate entities from bacteria.
    • In the late 1930s, Stanley, Bawden, and Pirie crystallized the tobacco mosaic virus.
    • This proved viruses were composed of protein and nucleic acid.

    Virus Reproduction/Replication

    • Viral reproduction is a 5-step process: Attachment, Penetration, Synthesis, Self-assembly, and Release.
    • Attachment: the virion attaching to a susceptible host cell.
    • Penetration: the virion or its nucleic acid enters the host cell.
    • Synthesis: viral genes are transcribed and translated; host cell machinery is used for replication and protein synthesis.
    • Self-assembly: the components of the capsid will self-assemble around the nucleic acid.
    • Release: mature virions are released from the host cell.

    Virus Cultivation

    • Viruses cannot be cultured like bacteria or eukaryotic microorganisms.
    • They require a living host.
    • Tissue cultures, embryonated eggs, bacterial cultures, are used for cultivation.
    • Sites of animal viral infection can be characterized by cytopathic effects, such as pocks and plaques.
    • Phages produce plaques on bacterial lawns.
    • Plant viruses cause localized necrotic lesions in plant tissues.
    • Fertilized chicken eggs are also used for viral cultivation; the shell is disinfected, a hole drilled, and virus injected into the allantoic cavity.
    • The egg is then incubated.

    Virus Quantification

    • Viruses can be counted directly using electron microscopy.
    • The hemagglutination assay is an indirect method of quantifying viruses.
    • Plaque assay: a clear area of lysis from viral replication; used to calculate virus infectious units.
    • Whole animal methods are involved in calculating lethal dose and infectious dose.

    Viruses Taxonomy

    • The ICTV (International Committee on Taxonomy of Viruses) developed a uniform classification system.
    • Viruses are placed in orders, families, subfamilies, and genera.
    • Viruses are classified based on the type and strandedness of their nucleic acids, and presence or absence of an envelope.
    • Baltimore classification system categorizes viruses based on their genome type and mechanism to create mRNA.

    Virus Diversity and Other Acellular Agents

    • There is an array of virus types, which are diverse in structure and genome type.
    • Examples include bacteriophages (viruses that infect bacteria).
    • These may have complex structures and diverse types of nucleic acids.
    • Mycoviruses (fungal viruses).
    • These can contain either dsDNA or dsRNA.
    • Viruses of protists also exist; these viruses have large dsDNA genomes.
    • Insect viruses often contain granular inclusion bodies that aid in viral transmission.
    • Some utilize insects as primary hosts.

    Viroids and Virusoids

    • Viroids are infectious RNA molecules.
    • These are easier to classify compared to viruses.
    • Virusoids are also infectious RNA, but require a helper virus to replicate.

    Prions

    • Prions are proteinaceous agents, associated with degenerative nervous system disorders.
    • Evidence suggests prions have two forms: abnormal, infectious form, and normal cellular form.
    • The abnormal form converts normal protein to the abnormal form.

    Vaccines and Antivirals

    • Vaccines are biological agents used to improve immunity to specific diseases.
    • Vaccines contain disease-causing microbe (attenuated or killed).
    • Antivirals are medications to combat viral infections.
    • These target specific stages of viral replication or the interaction of the virus with the host cell. There are different types of vaccines such as inactivated, attenuated, subunit and DNA vaccines.

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    Description

    Test your understanding of virology with this quiz covering key concepts such as viroids, prions, vaccine types, and virus structures. You'll encounter questions related to the characteristics and classifications of various viruses, including RNA viruses and SARS-CoV-2. Perfect for students studying microbiology or anyone interested in the intricacies of viral pathogens.

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