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Questions and Answers
What is the primary method of horizontal transmission of plant viruses?
What is the primary method of horizontal transmission of plant viruses?
Which of the following is true about viroids?
Which of the following is true about viroids?
What characterizes non-enveloped DNA viruses?
What characterizes non-enveloped DNA viruses?
Which diseases are associated with prions?
Which diseases are associated with prions?
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Which family of viruses is particularly known for causing hyperplastic lesions?
Which family of viruses is particularly known for causing hyperplastic lesions?
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How do viral particles facilitate systemic infection in plants?
How do viral particles facilitate systemic infection in plants?
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What distinguishes the two subfamilies of Papovaviridae?
What distinguishes the two subfamilies of Papovaviridae?
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Which statement about RNA genomes of plant viruses is accurate?
Which statement about RNA genomes of plant viruses is accurate?
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What is the primary mode of transmission for HSV-1?
What is the primary mode of transmission for HSV-1?
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Which statement about HSV-2 is accurate?
Which statement about HSV-2 is accurate?
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What typically occurs in immunocompetent individuals during HSV infection?
What typically occurs in immunocompetent individuals during HSV infection?
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What is a possible complication of HSV infection in the eye?
What is a possible complication of HSV infection in the eye?
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What symptom is commonly associated with primary infections of the upper body caused by HSV?
What symptom is commonly associated with primary infections of the upper body caused by HSV?
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Which type of herpes simplex virus is most commonly associated with lesions below the waist?
Which type of herpes simplex virus is most commonly associated with lesions below the waist?
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Which of the following is a significant risk if HSV infection spreads to the CNS?
Which of the following is a significant risk if HSV infection spreads to the CNS?
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Primary genital infections with HSV usually present as:
Primary genital infections with HSV usually present as:
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Which protein is not one of the four proteins encoded by the hepatitis B viral DNA?
Which protein is not one of the four proteins encoded by the hepatitis B viral DNA?
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Which body fluid is NOT a source of hepatitis B virus transmission?
Which body fluid is NOT a source of hepatitis B virus transmission?
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What is the typical incubation period for hepatitis B infection?
What is the typical incubation period for hepatitis B infection?
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What characterizes the acute, icteric phase of hepatitis B infection?
What characterizes the acute, icteric phase of hepatitis B infection?
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Which of the following best describes the primary infection response in most individuals to hepatitis B?
Which of the following best describes the primary infection response in most individuals to hepatitis B?
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What is the primary reason for the public health concern regarding hepatitis B?
What is the primary reason for the public health concern regarding hepatitis B?
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In which demographic is hepatitis B primarily a disease?
In which demographic is hepatitis B primarily a disease?
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What is the viral titer level indicated for a patient infected during acute hepatitis B infection?
What is the viral titer level indicated for a patient infected during acute hepatitis B infection?
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What is the primary mode of transmission for the rubella virus?
What is the primary mode of transmission for the rubella virus?
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Which of the following is a consequence of congenital rubella infection?
Which of the following is a consequence of congenital rubella infection?
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What distinguishes rubella from measles (rubeola)?
What distinguishes rubella from measles (rubeola)?
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What is the incubation period for rubella virus infection?
What is the incubation period for rubella virus infection?
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Which of the following is an appropriate preventive measure for congenital rubella?
Which of the following is an appropriate preventive measure for congenital rubella?
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Which statement about the clinical features of rubella is true?
Which statement about the clinical features of rubella is true?
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What complication can occur if rubella infection happens early in pregnancy?
What complication can occur if rubella infection happens early in pregnancy?
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What is a major cause of post-transfusion hepatitis?
What is a major cause of post-transfusion hepatitis?
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What are the first areas on the body where rashes develop in a rubella infection?
What are the first areas on the body where rashes develop in a rubella infection?
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Which of the following is a common cutaneous disease associated with HCV infection?
Which of the following is a common cutaneous disease associated with HCV infection?
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How does hepatitis C virus primarily damage liver cells?
How does hepatitis C virus primarily damage liver cells?
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Which of the following statements is true regarding RNA viruses and chronic infections?
Which of the following statements is true regarding RNA viruses and chronic infections?
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Which condition might prompt testing for HCV in a patient?
Which condition might prompt testing for HCV in a patient?
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What characteristic of coronaviruses gives them their name?
What characteristic of coronaviruses gives them their name?
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Which type of virus has the largest genome among RNA viruses?
Which type of virus has the largest genome among RNA viruses?
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Approximately what percentage of HCV infections present with acute hepatitis symptoms?
Approximately what percentage of HCV infections present with acute hepatitis symptoms?
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What happens during the latent period of HIV infection?
What happens during the latent period of HIV infection?
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Which of the following symptoms is NOT associated with the clinical complications during the latent period of HIV infection?
Which of the following symptoms is NOT associated with the clinical complications during the latent period of HIV infection?
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What is the likely outcome when CD4+ count falls below 200/μl in an HIV-infected patient?
What is the likely outcome when CD4+ count falls below 200/μl in an HIV-infected patient?
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What characterizes the replication of virus isolated during the latent period compared to that isolated later?
What characterizes the replication of virus isolated during the latent period compared to that isolated later?
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What can stimulate the immune response and activate HIV replication?
What can stimulate the immune response and activate HIV replication?
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Which of the following is an example of an opportunistic infection that may occur during the latent period?
Which of the following is an example of an opportunistic infection that may occur during the latent period?
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What occurs as the immune system weakens in the progression towards end-stage AIDS?
What occurs as the immune system weakens in the progression towards end-stage AIDS?
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During which phase do patients with HIV experience a relatively stable, low level of virus production?
During which phase do patients with HIV experience a relatively stable, low level of virus production?
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Study Notes
Virology: Chapter 1: The Virus
- Viruses are small infectious agents that replicate only inside living cells of other organisms.
- Viruses can infect all life forms, from animals and plants to microorganisms, including bacteria and archaea.
- Viruses are categorized based on their genetic material: DNA or RNA.
Introduction
- Viruses are too small to be seen with a light microscope.
- They are obligate intracellular parasites, meaning they require a host cell to multiply.
- Viruses are filterable agents, able to pass through filters that retain back bacteria.
- Viruses contain a nucleic acid genome, packaged within a protein coat (capsid). Sometimes, an envelope of lipids, proteins, and carbohydrates surrounds the capsid.
- Viruses replicate using the host cell's machinery.
- They do not replicate by cell division (binary fission).
- Generally, they lack enzymes for their own metabolism.
Bacteria vs. Viruses
- Key difference: Bacteria are living cells, while viruses are non-living entities.
- Bacteria have cells, viruses do not.
- Common attribute: Both can cause disease.
- Treatment: Antibiotics target bacteria, while vaccines and antiviral medications help fight viruses.
Structure of a Virus
- The virion consists of a nucleic acid core (genome) surrounded by a protein coat (capsid).
- The capsid and nucleic acid together are known as the nucleocapsid.
- Some viruses are enveloped.
Basic Virus Structure
- DNA or RNA + protein capsid = Nucleocapsid.
- Nucleocapsid + lipid membrane and glycoproteins = Enveloped virus
- Nucleocapsid without the envelope = Non-enveloped virus, or naked virus.
Viral Structure
- A virion is an intact, infectious viral particle.
- The capsid is composed of protein subunits called capsomeres.
- Viral symmetry can be icosahedral or helical.
- Some have an envelope (derived from the host cell membrane).
- Viruses contain a genome (instructions for viral functions) comprised of DNA or RNA, which may be single- or double-stranded, linear or circular.
Viral Classification
- Viruses are classified based on the structure of their capsid.
- Helical viruses: rod-shaped capsids (e.g., rabies virus, Ebola virus)
- Polyhedral viruses: many-sided capsids (icosahedral) (e.g., adenovirus)
- Enveloped viruses: covered by an envelope (e.g., influenza virus, herpes simplex virus)
- Complex viruses: complicated structures (e.g., bacteriophages)
1-The Capsid
- The nucleic acid of the virus is surrounded by a protein coat called the capsid.
- The capsid is made of protein subunits called capsomeres.
- The arrangement of capsomeres is characteristic of a specific virus type.
- The capsid protects the viral nucleic acid and aids in attachment or entry into host cells.
2- The Envelope
- The viral envelope usually consists of lipids, proteins, and glycoproteins often derived from the host cell membrane.
- Enveloped viruses can be sensitive to heat and detergents, while non-enveloped viruses tend to be more stable.
- Envelopes aid in protection of the viral genome and host cell entry.
3- Viral Symmetry
- Viruses are classified by their capsid symmetry.
- Icosahedral symmetry: The capsid is composed of equilateral triangles (e.g., adenoviruses, herpesviruses).
- Helical symmetry: The capsid forms a helix around the nucleic acid (e.g., influenza virus, rabies virus). These viruses can have one or more RNA strings within the capsid.
- Complex symmetry: A combination of both shapes described above, or a unique geometry (e.g., bacteriophages).
4- Viral Nucleic Acid, Proteins and Lipids
- The viral genome is composed of either DNA or RNA, but never both.
- Viral DNA can be linear or circular.
- Viral RNA can be positive-sense, negative-sense, both, or ambiguous
- Viruses may contain more than one piece of nucleic acid.
- Viral proteins form the capsid, and some enveloped viruses contain lipids embedded in these membranes.
- The viral proteins determine the virus's characteristics and allow it to infect more cells.
1-The Capsid
- The capsid is a protein coat surrounding the virus's genome.
- It protects the genome and facilitates the virus's attachment and entry into host cells.
- The capsid structure can be icosahedral, helical, or complex.
Viral Multiplication (Bacteriophages)
- Viruses reproduce by taking control of the host cell's metabolic machinery
- Different replication cycles (lysogenic and lytic) exist for different types of viruses.
- Lytic cycle: viral components replicate in the host cell and lyse the host cell to release the progeny virions
- Lysogenic cycle: the phage DNA is incorporated into the host's DNA sequence (becoming a prophage) and remains inactive until conditions trigger the cell's replication to also produce progeny viruses. This maintains the virus without harming the host cell
Viral Multiplication (Animal Viruses)
- Viruses often enter host cells by endocytosis or membrane fusion following attachment and/or penetration and uncoating, instead of direct genome injection
- The viruses replicate in the cytoplasm or nucleus following uncoating.
- The virus replicates via reverse transcription in some cases (e.g., HIV).
Replication Cycles in Animal Viruses
- Attachment (adsorption), Penetration, Transcription/Replication, Translation, Assembly, Release (or budding) describe the general phases.
- Differences exist in specific events, especially in regard to where the virion replication takes place, and how the virus is released
- Most viruses leave the host cell by lysis, some enveloped viruses bud, some viruses maintain latency.
2- The Envelope
- Many animal viruses have an outer envelope derived from the host cell membrane.
- Viral glycoproteins are embedded in the viral envelope and can aid in host cell recognition and entry into the cell.
3- Viral Symmetry
Properties of Human DNA Viruses
- Summarize structural types (e.g., shapes - spherical, brick-shaped ,polyhedral) viral size and genome nature as well as their classification (families, genera, and examples).
Properties of Human RNA Viruses
- Summarize structural (e.g., shapes = spherical, bullet shaped) types, size and genome nature; as well as their classification ( families, genera, and examples).
Replication Cycles in Animal Viruses
2- The Envelope
3- Viral Symmetry
4- Viral Nucleic Acid, Proteins and Lipids
Lysis
Replication Cycles in Animal Viruses
2- The Envelope
3- Viral Symmetry
4- Viral Nucleic Acid, Proteins and Lipids
Viral Nucleic Acid, Proteins and Lipids
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Description
Explore the fascinating world of viruses in this quiz based on Chapter 1 of Virology. Learn about their characteristics, replication methods, and how they differ from bacteria. Test your knowledge on the smallest infectious agents that rely on host cells for survival.
