Virology Quiz: Virus Characteristics and Types
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Questions and Answers

What type of nucleic acid do adenoviruses contain?

  • Single-stranded linear RNA
  • Single-stranded circular RNA
  • Double-stranded linear DNA (correct)
  • Double-stranded circular DNA

    • Which virus is associated with causing infectious mononucleosis?

  • Poxvirus
  • Cytomegalovirus
  • Epstein-Barr virus (correct)
  • Adenovirus

    • What is a key feature of hepadnaviruses?

  • They contain a more complex capsid symmetry than other viruses.
  • The complete strand of their DNA is a covalently closed circle.
  • They have a double-stranded circular DNA genome with a missing part. (correct)
  • They have a single-stranded linear DNA genome.

    • Which family of viruses is known for causing latent infections?

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

    What is the significance of the smallpox virus in the context of poxviruses?

    <p>It is used in the smallpox vaccine.</p> Signup and view all the answers

    Which of the following viruses has the largest size based on the provided information?

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

    What type of genome do picornaviruses have?

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

    Which of the following correctly describes caliciviruses?

    <p>They are naked viruses with a single-stranded linear RNA genome.</p> Signup and view all the answers

    What characterizes enveloped viruses compared to naked viruses?

    <p>They have a lipid-containing membrane surrounding the nucleocapsid.</p> Signup and view all the answers

    Which group of viruses is characterized by containing double-stranded DNA?

    <p>Group I: dsDNA.</p> Signup and view all the answers

    Which of the following viruses is part of the papovavirus family?

    <p>JC virus.</p> Signup and view all the answers

    What is the particle size of papovaviruses?

    <p>55 nm.</p> Signup and view all the answers

    Which of the following statements about the envelope of viruses is true?

    <p>The envelope is formed from host cell membranes, replacing host proteins.</p> Signup and view all the answers

    Which type of virus has an internal complex symmetry?

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

    Which of the following viruses is an example of a naked virus?

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

    What is the first step in the virus replication cycle?

    <p>Virus attachment to the host cell.</p> Signup and view all the answers

    What forms the basis for division into genera and species within a virus family?

    <p>Differences in host range and amino acid sequences</p> Signup and view all the answers

    What type of viral genome can be used directly as a template for protein synthesis?

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

    Which of the following statements about capsid symmetry is TRUE?

    <p>Icosahedral capsids consist of structural subassemblies called capsomers.</p> Signup and view all the answers

    What is the structure formed by the association of proteins and viral nucleic acid in helical symmetry?

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

    How are capsomers in an icosahedral capsid related?

    <p>They are hydrogen-bonded to each other.</p> Signup and view all the answers

    Which of the following characteristics is NOT associated with a helical capsid?

    <p>Made up of multiple polypeptide types</p> Signup and view all the answers

    What role do nucleic acids play in the structure of an icosahedral capsid?

    <p>They are housed within the empty space of the capsid.</p> Signup and view all the answers

    What is the most common form of viral genome encountered in nature?

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

    Which viruses are classified as important human pathogens?

    <p>Measles, Mumps, Parainfluenza, and Respiratory Syncytial viruses</p> Signup and view all the answers

    What is the shape of rhabdoviruses?

    <p>Bullet-shaped</p> Signup and view all the answers

    What type of RNA do filoviruses contain?

    <p>Single-stranded, linear, nonsegmented negative-polarity RNA</p> Signup and view all the answers

    Which two viruses are associated with filoviruses as human pathogens?

    <p>Ebola and Marburg</p> Signup and view all the answers

    What characteristic does the term 'corona' refer to in coronaviruses?

    <p>The prominent halo of spikes protruding from the envelope</p> Signup and view all the answers

    What was the fatality rate of SARS during its outbreak in 2002?

    <p>9%</p> Signup and view all the answers

    Which of the following was identified as a reservoir for CoV-SARS?

    <p>Horseshoe bats</p> Signup and view all the answers

    Which virus is classified under the genus hepevirus?

    <p>Hepatitis E virus</p> Signup and view all the answers

    Which virus emerged in 2020 and is known to cause COVID-19?

    <p>SARS-CoV-2</p> Signup and view all the answers

    What is the structure of reoviruses?

    <p>Naked with two icosahedral capsid coats</p> Signup and view all the answers

    Which of the following is a main human pathogen of flaviviruses?

    <p>Dengue virus</p> Signup and view all the answers

    What characteristic distinguishes retroviruses from other virus families?

    <p>They have a diploid RNA genome.</p> Signup and view all the answers

    Which virus is known as the main human pathogen in the orthomyxovirus family?

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

    Which groups are included in the family of retroviruses?

    <p>Oncoviruses and lentiviruses</p> Signup and view all the answers

    Which characteristic is true for paramyxoviruses?

    <p>They are enveloped with a helical nucleocapsid.</p> Signup and view all the answers

    Which type of vaccine is the Pfizer-BioNTech COVID-19 vaccine classified as?

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

    Which of the following viruses is classified as an RNA virus without an envelope?

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

    What is the genomic structure of parvoviruses?

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

    Which of the following vaccines is classified as a viral vector vaccine?

    <p>Oxford-AstraZeneca vaccine</p> Signup and view all the answers

    What type of RNA do reoviruses possess?

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

    Which vaccine uses inactivated virus technology?

    <p>Sinopharm vaccine</p> Signup and view all the answers

    Which classification includes DNA viruses with an envelope?

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

    What type of RNA is found in coronaviruses?

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

    Study Notes

    Medical Important Viruses

    • Viruses are infectious agents composed of a genome (RNA or DNA, but not both) and a protein capsid that protects the genome.
    • Many viruses have additional structures, like a lipid envelope, further distinguishing them.

    Virion

    • A complete virus particle is called a virion.
    • It serves as a delivery system, protecting the viral genome and enabling the virus to attach to host cells.
    • The virion may include enzymes necessary for viral replication, which is intracellular.
    • Pathogenicity varies within related virus groups, leading to different clinical pathologies.

    Virus Structure

    • Viruses are significantly smaller than the cells they infect (100-1000-fold).
    • Virion sizes vary: the smallest are around 20 nm (parvoviruses) and the largest about 300 nm (poxviruses).
    • Viruses pass through filters designed to trap bacteria.

    Virus Classification

    • Viruses are categorized into families, sometimes subfamilies, based on the type and structure of the viral nucleic acid, viral replication strategy, and symmetry of their capsids (helical or icosahedral), and the presence or absence of a lipid envelope.
    • Within a virus family, variations in properties like host range, serologic reactions, and amino acid sequences of viral proteins serve as the basis for further division into genera and species.

    Virus Genome

    • Viral genomes can be either DNA or RNA, and either single-stranded (ss) or double-stranded (ds).
    • Single-stranded RNA viruses are categorized into positive- or negative-polarity.
    • Positive-polarity RNA serves directly as a template for protein synthesis, while negative-polarity RNA requires an additional step to produce a viable template.
    • There are both RNA and DNA virus families.

    Viral Capsid Symmetry

    • The protein shell enclosing the viral genome (capsid) has either helical or icosahedral symmetry.
    • The capsid's structure results from multiple copies of a single polypeptide or a few different polypeptides.

    Helical Symmetry

    • Capsids with helical symmetry (rod-shaped or coiled) are comprised of repeated, identical protein units (protomers) linked together.
    • These protomers bind to one another via hydrogen bonds. forming a helical structure.
    • This structure encloses the viral nucleic acid, creating a helical nucleocapsid.

    Icosahedral Symmetry

    • Capsids with icosahedral symmetry (spheres) are more complex, with multiple polypeptide types grouped into subassemblies called capsomers.
    • The capsomers form a 20-faced structure (icosahedron) with a central void.
    • The nucleic acid genome is found within the icosahedral structure's internal space.

    Viral Envelope

    • An envelope, a lipid-containing membrane, frequently surrounds the nucleocapsid (in enveloped viruses).
    • The virus envelope is derived from host cell membranes, but the virus-specific proteins confer virus-specific antigenicity on the virus particle.
    • Enveloped viruses have a flexible and coiled nucleocapsid within the envelope, typically appearing roughly spherical.

    Viral Replication

    • Viral replication follows a cycle of attachment, penetration/uncoating, gene expression/replication, assembly and finally, release of viral progeny.

    Baltimore Classification of Medically Important Viruses

    • Viruses are categorized into 7 groups based on their DNA or RNA structure/replication mechanisms.

    DNA Viruses

    • The three naked (non-enveloped) icosahedral virus families (parvoviruses, papovaviruses, and adenoviruses) are categorized by increasing size.
    • The hepadnavirus family (including hepatitis B virus) and herpesviruses are enveloped icosahedral viruses.
    • The poxviruses, the largest, have a complex internal symmetry.

    Papovaviruses

    • These are naked icosahedral viruses with double-stranded circular DNA.
    • Three human papovaviruses: papilloma, polyoma, and SV40 viral infections, cause various human diseases.

    Adenoviruses

    • Adenoviruses are naked icosahedral viruses with double-stranded linear DNA.
    • They cause mild respiratory diseases, pharyngitis, and infections in other locations (ocular illnesses).

    Hepadnaviruses

    • These are enveloped viruses with an icosahedral DNA core surrounded by an envelope.
    • Their unusual DNA structure, mostly double-stranded but with a single-stranded region, includes hepatitis B.

    Herpesviruses

    • These are enveloped viruses with an icosahedral capsid and double-stranded linear DNA.
    • Notable examples of human pathogens include herpes simplex virus types 1 and 2, varicella-zoster virus, cytomegalovirus, and Epstein-Barr virus

    Poxviruses

    • These are the largest viruses, possessing a brick-like shape, an envelope, and complex capsid symmetry.
    • A prominent example is the smallpox virus.

    RNA Viruses

    • The three naked icosahedral families (picornaviruses, caliciviruses, and reoviruses) are listed first, followed by three enveloped icosahedral families.
    • The other eight families are enveloped helical viruses, further subdivided into groups with single-stranded linear (first 5) or single-stranded circular (last 3) genomes.

    Picornaviruses

    • Smallest RNA viruses (28 nm).
    • Naked, icosahedral, and single-stranded RNA.
    • Poliovirus, coxsackievirus, echovirus, hepatitis A virus, and rhinoviruses are human pathogens.

    Caliciviruses

    • Naked, icosahedral RNA viruses (38 nanometers). Single-stranded, linear, non-segmented, positive-polarity RNA.
    • Contagious diarrhea (often called Norwalk virus) can be caused by these viruses. Hepatitis E virus is a related pathogen.

    Reoviruses

    • Naked viruses with icosahedral capsid coats and double-stranded, linear RNA.
    • Rotavirus, causing diarrhea, is one example.

    Flaviviruses

    • Enveloped viruses with an icosahedral capsid, single-stranded, linear, non-segmented, positive-polarity RNA.
    • These include hepatitis C, yellow fever, dengue, West Nile, St. Louis encephalitis, and Japanese encephalitis viruses.

    Togaviruses

    • Enveloped viruses with icosahedral capsids and single-stranded, linear, non-segmented, positive polarity RNA.
    • Alphaviruses cause encephalitis (western and eastern), and rubella (German measles) virus is also in this family.

    Retroviruses

    • Enveloped viruses with icosahedral capsids and two identical, single-stranded, linear, positive polarity RNA strands.
    • They use reverse transcriptase to convert their RNA genome to DNA for integration into the host genome.
    • Examples include human T-cell leukemia virus (HTLV) and human immunodeficiency virus (HIV).

    Orthomyxoviruses

    • These enveloped viruses have helical nucleocapsids and eight segments of nonsegmented, negative polarity RNA.
    • Influenza viruses.

    Paramyxoviruses

    • Enveloped RNA viruses with helical nucleocapsids and nonsegmented, negative polarity RNA.
    • Measles, mumps, parainfluenza, and respiratory syncytial viruses cause significant illnesses.

    Rhabdoviruses

    • These bullet-shaped viruses have envelopes and helical nucleocapsids of nonsegmented, negative polarity RNA.
    • Rabies virus is the single most notable pathogen.

    Filoviruses

    • Enveloped viruses with helical nucleocapsids and single-stranded RNA.
    • Ebola and Marburg viruses cause severe hemorrhagic fevers.

    Coronaviruses

    • Enveloped viruses with helical nucleocapsids and single-stranded, linear, nonsegmented, positive polarity RNA.
    • Coronaviruses like SARS-CoV-2 (COVID-19), SARS-CoV, and MERS-CoV are significant.

    Viral Diseases

    • Coronaviruses are a significant cause of the common cold.
    • Emerging viral outbreaks include Severe Acute Respiratory Syndrome (SARS) in 2002, Middle East Respiratory Syndrome (MERS) in 2012, and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in 2019.

    COVID-19 Symptoms

    • Common symptoms include fever, tiredness, dry cough, aches, pains, nasal congestion, runny nose, sore throat, and diarrhea.
    • Severe symptoms include difficulty breathing and involve individuals with underlying health conditions (asthma, compromised immune systems, and pre-existing health conditions).

    COVID-19 Transmission

    • The virus can be transmitted through the air, via droplets or through contaminated surfaces.

    COVID-19 Prevention

    • Frequent hand-washing, avoidance of contact with sick individuals, use of facemasks. avoiding crowded spaces, are ways to prevent the spread of the virus.

    COVID-19 Molecular and Antibody Tests

    • Nucleic acid tests detect viral genetic material (RNA).
    • Antibody tests detect the presence of antibodies indicating a prior infection.

    COVID-19 Vaccines

    • Multiple vaccines (mRNA, inactivated virus, viral vector) are currently available to prevent infection.

    Virus Variants

    • Virus variants (e.g., Omicron, Alpha, Beta, Gamma, Delta) emerge from mutations; some display increased transmission potential, different virulence, variations in symptoms, or a different response to therapies or vaccines.

    Study Notes and References

    • This is a summary of viral information from various sources.
    • Specific references for further study are also available from the provided materials.

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    Medical Important Viruses - PDF

    Description

    Test your knowledge on various viruses and their characteristics with this quiz. From adenoviruses to hepadnaviruses, explore the different types, structures, and replication cycles of these pathogens. Ideal for students studying virology and infectious diseases.

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