Virology Fundamentals Quiz
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Questions and Answers

What is the approximate diameter range of most viruses?

  • 100 μm - 500 μm
  • 10 nm - 700 nm (correct)
  • 1 mm - 5 mm
  • 1 μm - 10 μm

    • Who is credited with first identifying the 'filterable virus', later known as the tobacco mosaic virus?

  • Martinus Beijerinck
  • Dmitri Ivanovsky (correct)
  • Robert Koch
  • Louis Pasteur

    • Thomas Milton Rivers' 1920s book on filtrable viruses emphasized which key characteristic of viruses?

  • Viruses are easily visible under a light microscope.
  • Viral reproduction is independent of host cells.
  • Viruses are obligate parasites, dependent on living cells for reproduction. (correct)
  • Viruses can be cultured in nutrient-rich broths like bacteria.

    • What was the original purpose of the Chamberlain filter, which later became crucial in virology experiments?

    <p>To remove bacteria from drinking water. (A)</p> Signup and view all the answers

    In the tobacco mosaic virus experiment using the Chamberlain filter, what critical observation indicated the infectious agent was not a bacterium?

    <p>The filtrate remained infectious even after bacteria were removed. (A)</p> Signup and view all the answers

    Pasteur's experiments with rabies pathogen and the Chamberlain filter primarily demonstrated what about the rabies-causing agent?

    <p>It was smaller than what could be seen with a light microscope and filterable. (D)</p> Signup and view all the answers

    Viruses are known to infect a wide range of organisms. Which of the following groups are all known to be infected by viruses?

    <p>Plants, animals, protists, archaea, and bacteria. (C)</p> Signup and view all the answers

    The experiments using the Chamberlain filter in the late 19th century primarily addressed which fundamental question about the nature of infectious agents like the tobacco mosaic virus and rabies pathogen?

    <p>Whether these agents were bacteria or something smaller. (C)</p> Signup and view all the answers

    Approximately how many bacteriophage particles are estimated to exist in the world's waters?

    <p>10^30 (B)</p> Signup and view all the answers

    If a bacteriophage weighs a femtogram (10^-15 grams), what is the approximate weight of all bacteriophages in the world's waters in kilograms?

    <p>10^12 kg (C)</p> Signup and view all the answers

    How does the weight of all bacteriophages in the world's waters compare to the weight of the human population?

    <p>Greater than the weight of the world population. (B)</p> Signup and view all the answers

    Which of the following is a virus known to infect bacteria?

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

    What is the approximate number of viruses in a liter of seawater?

    <p>Greater than the number of people on Earth (B)</p> Signup and view all the answers

    Which of the following is NOT mentioned as a virus that can cause lifelong infections?

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

    According to Dr. Thompson's lecture, what do we regularly do with billions of virus particles?

    <p>Eat and breathe them in (C)</p> Signup and view all the answers

    What is the main topic of Dr. Craig Thompson's lecture?

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

    Which of the following best describes the genetic material of a virus?

    <p>Either DNA or RNA, but never both (B)</p> Signup and view all the answers

    What is a key structural difference between viruses and bacteria regarding protein synthesis?

    <p>Viruses lack ribosomes, while bacteria have them (D)</p> Signup and view all the answers

    What size are viruses are typically observed at under an Electron Microscope?

    <p>20-400nm (B)</p> Signup and view all the answers

    The Baltimore classification system categorizes viruses primarily based on:

    <p>Their genome type and mRNA synthesis method (C)</p> Signup and view all the answers

    Which statement is true regarding the Baltimore classification of viruses?

    <p>It categorizes viruses into families based on genome type and replication strategy. (D)</p> Signup and view all the answers

    What technology enabled scientists to definitively identify viruses as microorganisms composed of proteins and nucleic acids?

    <p>Electron microscopy (A)</p> Signup and view all the answers

    Which virus class utilizes reverse transcriptase to create a DNA copy from its RNA genome?

    <p>ssRNA-RT viruses (C)</p> Signup and view all the answers

    Which of the following is NOT a characteristic used to differentiate between bacteria and viruses?

    <p>Presence or absence of an envelope (A)</p> Signup and view all the answers

    What was the key finding from the Hershey-Chase experiment concerning the genetic material in bacteriophages?

    <p>DNA carries the genetic information. (A)</p> Signup and view all the answers

    What primarily distinguishes Class VI (ssRNA-RT) viruses in the Baltimore classification?

    <p>A single-stranded RNA genome that uses reverse transcriptase (B)</p> Signup and view all the answers

    In the Hershey-Chase experiment, how did the researchers introduce radioactive isotopes into the bacteriophages?

    <p>Growing bacteria in media containing the isotopes (C)</p> Signup and view all the answers

    What technique was employed in the Hershey-Chase experiment to detach phage coats from the bacteria?

    <p>Agitation in a blender (A)</p> Signup and view all the answers

    After separating phage coats from bacteria in the Hershey-Chase experiment, what method was used to further isolate the components?

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

    Which radioactive isotope remained present in the bacterial progeny after infection by labeled phages in the Hershey-Chase experiment?

    <p>Phosphorus-32 (D)</p> Signup and view all the answers

    What was the significance of using radioactive sulfur in the Hershey-Chase experiment?

    <p>To label the phage proteins (C)</p> Signup and view all the answers

    Who first visualized viruses using an electron microscope?

    <p>Helmut Ruska (A)</p> Signup and view all the answers

    What characterizes a susceptible and permissive cell in viral infections?

    <p>It can take up the virus and allow for its replication. (D)</p> Signup and view all the answers

    How does a chronic infection differ from an acute infection?

    <p>Acute infections involve lasting immunity, whereas chronic infections have prolonged viral presence. (C)</p> Signup and view all the answers

    Which factor prevents viral genome elimination in persistent infections?

    <p>Viral genome integrates into or remains as episomal molecules in host cells (C)</p> Signup and view all the answers

    What mechanism allows some viruses to evade the host immune system?

    <p>Restricted expression of the viral genome and antigenic variation (A)</p> Signup and view all the answers

    Which scenario best exemplifies a latent viral infection?

    <p>A primary infection followed by restricted viral gene expression and potential reactivation. (B)</p> Signup and view all the answers

    What is a primary mechanism by which influenza viruses cause cytopathy?

    <p>Lysis of ciliated and mucus-secreting respiratory epithelial cells (D)</p> Signup and view all the answers

    Which part of the host protective response is crucial for future immunity against influenza?

    <p>Antibody production (D)</p> Signup and view all the answers

    In the pathogenesis of varicella, which step primarily involves the infection of T cells?

    <p>Stability in the body compartment (C)</p> Signup and view all the answers

    Which aspect of varicella pathogenesis is responsible for latent infection?

    <p>Latent infection in neurons (A)</p> Signup and view all the answers

    Which route of viral entry is shared by both influenza and varicella?

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

    Flashcards

    Virus Characteristics

    Key elements that define a virus include its structure, infection methods, and life cycle.

    Experiments Identifying Viruses

    Key experiments such as the filtration method helped identify viruses as infectious agents.

    Viral Structure

    Viruses have a simple structure consisting of genetic material surrounded by a protein coat.

    Infectious Cycle

    The process through which a virus infects a host, replicates, and spreads.

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    Latency in Viruses

    A phase where the virus remains dormant in the host without causing symptoms.

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    Chronic Active Infection

    A persistent viral infection where symptoms continue over time.

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    Viral Pathogenesis

    The development and effects of disease caused by viral infections.

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    Human Virome

    The collection of viruses that live in and on the human body.

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    Electron Microscope

    A tool that allows scientists to visualize viruses and other small structures.

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    Hershey-Chase Experiment

    An experiment demonstrating that DNA is the genetic material of viruses.

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    Bacteriophages

    Viruses that infect bacteria, used in the Hershey-Chase experiment.

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    Radioactive Isotopes

    Elements used to label genetic material in the Hershey-Chase experiment.

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    Lysing Bacteria

    Breaking open bacteria to release viral progeny after infection.

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    Nucleic Acids

    Molecules that carry genetic information in viruses (DNA/RNA).

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    Separation Procedure

    Method to separate phage coats from bacteria in the Hershey-Chase experiment.

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    Genetic core of viruses

    The central part of a virus containing either DNA or RNA, never both.

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    Protein coat (capsid)

    A protective protein shell surrounding the virus's genetic material, made of subunits called capsomeres.

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    Virus envelope

    A lipid layer surrounding some viruses, derived from the host cell membrane.

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    Obligate intracellular parasites

    Viruses must infect a host cell to reproduce and survive, unlike free-living bacteria.

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    Baltimore classification

    A system categorizing viruses based on genome type and mRNA synthesis method.

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    dsDNA viruses

    Double-stranded DNA viruses, including types like Adenoviruses and Herpesviruses.

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    ssRNA viruses

    Single-stranded RNA viruses categorized into (+)sense and (–)sense types, like Picornaviruses.

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    Retroviruses

    A type of virus that uses reverse transcriptase to convert RNA into DNA within its lifecycle.

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    Types of Cells Infected by Viruses

    Viruses can infect plant, animal, protist, archaea, and bacteria cells.

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    Size Range of Viruses

    Viruses have a diameter range from 10nm to 700nm, with filoviruses up to 1400nm long.

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    Origin of the Term 'Virus'

    The term 'virus' originally meant poison, first used in the 1920s.

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    Discovered Tobacco Mosaic Virus

    The first filterable virus, discovered by Ivanovsky in 1892, initially thought to be a toxin.

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    Significance of the Chamberlain Filter

    The Chamberlain Filter proved that viruses are smaller than bacteria and require a host to replicate.

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    First Animal Virus

    The first animal virus identified was the Foot & Mouth Disease virus in 1898.

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    Key Discovery: Influenza Virus

    The Influenza virus was identified in 1933, significant in virology history.

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    Impact of the Electron Microscope

    Invented in 1931, it allowed detailed visualization and study of viruses.

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    Influenza Host Cell Entry

    Influenza binds specifically to receptors in the respiratory tract to enter host cells.

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    Influenza Cytopathy

    Influenza causes lysis of ciliated and mucus-secreting respiratory epithelial cells.

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    Varicella Routes of Infection

    Varicella virus enters host via inhalation, infects tonsils and URT mucosa.

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    Immunopathology in Influenza

    Cytokines during influenza infection can cause symptoms like chills and aches.

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    Latent Infection in Varicella

    Varicella can remain dormant in neurons, usually in ganglia, causing latent infections.

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    Susceptible and Permissive Cells

    Cells that can take up a virus and allow it to replicate.

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    Acute Infection

    Primary infection often followed by lasting immunity and quick recovery.

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    Chronic/Persistent Infection

    Infection that follows a primary infection and lasts a long time, often with symptoms that linger.

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    Latent Infection

    Infection with restricted viral gene expression after the primary infection, often reactivating later.

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    Pathogenesis

    The manner of development of a disease, including how it progresses.

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    Study Notes

    Introduction to Virology, Lecture 1

    • The lecture is titled "Introduction to Virology, Lecture 1" and was delivered by Dr. Craig Thompson, Assistant Professor of Molecular Pathology at Warwick Medical School.
    • Learning outcomes include describing key elements defining a virus, key experiments identifying viruses, the structure of viruses (with specific examples of influenza, varicella, and SARS-CoV-2), characteristics of the infectious cycle (examples of influenza, varicella, and SARS-CoV-2), viral infection terms (latency, chronic active, persistence), and the pathogenesis of viral infection (with emphasis on influenza and varicella).

    Viruses

    • Viruses infect all living things, and humans carry viral genomes as part of their genetic material.
    • There are more than 1030 bacteriophage particles in the world's waters.
    • A bacteriophage weighs a femtogram (10-15 g).
    • The weight of all the people in the UK is 5.29 x 109 kg.
    • The weight of the population of Europe is 3.512 x 1010 kg.
    • The weight of the world's population is 6.3 x 1011 kg.

    Viruses in a Liter of Seawater

    • A liter of seawater contains more viruses than there are people on Earth.
    • Abundance is measured by particle number.
    • Viruses comprise a significant portion of both abundance and biomass in seawater.

    Viruses – Infect Us

    • Some viruses, like herpes simplex, varicella zoster, cytomegalovirus, Epstein-Barr virus, and human herpesviruses 6, 7, and 8, persist for life.
    • The human virome lists specific virus types in various body fluids/organs.

    Viruses – Disease

    • Viruses cause a significant amount of human disease.
    • Top causes of death worldwide in 2019 included cardiovascular diseases, cancers, respiratory diseases, digestive diseases, and lower respiratory infections, among others.
    • Similarly, causes of death in children under five in 2019 included lower respiratory infections, neonatal preterm birth, neonatal asphyxia & trauma, and diarrheal diseases, among others.

    Viruses - Key Examples and Information

    • Annual deaths from influenza range from 250,000 to 600,000.
    • SARS-CoV-2 caused approximately 3,000,000 deaths per year.
    • HIV caused approximately 680,000 deaths per year.
    • Flaviviruses caused approximately 100,000 deaths per year.
    • Norovirus caused approximately 200,000 deaths per year.

    Infectious Diseases Impact

    • Infectious diseases have a significantly greater impact on lower and middle-income nations compared to higher-income countries.
    • Leading causes of death in several income groups are noted. This includes communicable and non-communicable causes.

    Gene Regulation and Viruses

    • Much of the human genome consists of integrated retroviruses in the form of transposons, specifically LINES and SINEs.
    • Viruses can insert themselves into the genome and regulate associated genes.
    • The placenta is formed from a viral protein called syncytin.
    • Viruses are being increasingly used as vaccine carriers (e.g., the ChadOx COVID-19 vaccine, based on an adenoviral vector).

    The Role of Viral Gene Regulation

    • Viral proteins are encoded by specific sections of viral genomes.
    • LTRs, (long terminal repeats), gag, pol, env, and LTRs have important roles in viral gene regulation and co-option affecting placenta formation.

    Key Experiments Identifying Viruses

    • Charles Chamberlain's filter experiments showed that viruses are smaller than bacteria, requiring a host for replication, and are microscopic in size.
    • The electron microscope allowed researchers to visualize viruses as microorganisms with organized proteins and nucleic acids.
    • Hershey-Chase experiments demonstrated that DNA, not protein, is the heritable material of viruses, proving DNA is the genetic material.

    Question 1: Microorganisms

    • How scientists discovered that viruses were microorganisms relates to the early experimental methods and tools available.

    The Structure of Viruses

    • Viruses have a genetic core consisting of DNA or RNA. Viruses either have DNA or RNA, but never both.
    • A protein coat, called a capsid, surrounds this core, with individual units called capsomeres.
    • Some viruses have an envelope, a lipid layer surrounding the capsid.

    Classification of Viruses

    • Viruses are classified based on various features visualized with electron microscopy (e.g., adenoviruses, Ebola viruses, herpes viruses, SARS viruses).
    • Examples of viruses illustrated in the classification include influenza, HIV, Papillomavirus, and more.

    Influenza Virus

    • An influenza virus contains antigenic sites on surface proteins (hemagglutinin and neuraminidase) vital for antibody recognition and neutralization when encountering influenza or influenza vaccine, preventing further infection.

    Differences between Bacteria and Viruses

    • Viruses are intracellular parasites, lacking ribosomes and metabolism; they rely on host cells.
    • In contrast, bacteria are typically free-living, possess ribosomes, and have distinct metabolic processes.

    Baltimore Classification

    • This system groups viruses based on their genome type (DNA or RNA, single-stranded or double-stranded) & mRNA synthesis method.

    Diversity of Viruses

    • DNA viruses have structures including poxviruses, adenoviruses, herpesviruses, and more.
    • RNA viruses have various structures, including coronaviruses, orthomyxoviruses, and retroviruses.

    Question 2: Baltimore Classification of Influenza

    • Influenza is classified as an RNA virus according to Baltimore classification.

    The Infectious Cycle

    • The infectious cycle encompasses all events within a virus-infected cell.
    • This includes receptor binding, cell entry, viral genome replication, viral protein synthesis, and virion assembly followed by release.

    Stages of Infection

    • The infection process includes attachment and entry, translation, genome replication, and release phases.

    Question 3 & 4: SARS-CoV-2 Entry Glycoprotein

    • SARS-CoV-2 utilizes a specific glycoprotein (spike protein) and a receptor (ACE2) to enter host cells.

    Viruses: Effects on Cells

    • Viral infections can cause cell death (cytopathic effect), transformation into tumor cells, and persistent/latent infections.

    Key Terms

    • Susceptible cells have functional receptors for a specific virus.
    • Resistant cells lack the necessary receptors.
    • Permissive cells have the capability for viral replication.

    Overview of Viral Infections

    • Various viral infections impacting different parts of the human body are listed.

    Viruses: Natural History of Infection

    • Acute infections typically resolve swiftly, followed by immunity.
    • Chronic infections persist, with either continuous viral replication or latency.

    Viruses: Persistence

    • Viruses may persist in host cells without causing cell death.
    • The persistence occurs through integration of viral genomes into host cells, episomal circular molecules or avoidance of the host-immune system.

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    Introduction to Virology Lecture 1 PDF

    Description

    Test your knowledge on key concepts in virology, including the characteristics of viruses and historic experiments involving the tobacco mosaic virus and rabies pathogen. This quiz covers foundational knowledge essential for understanding the nature of infectious agents.

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