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Questions and Answers
Which of the following statements is true regarding enveloped viruses compared to naked viruses?
Which of the following statements is true regarding enveloped viruses compared to naked viruses?
What type of symmetry is exhibited by all DNA viruses, except for poxvirus?
What type of symmetry is exhibited by all DNA viruses, except for poxvirus?
What is the role of surface proteins in viruses?
What is the role of surface proteins in viruses?
Which component of the virus serves to mediate interaction between nucleocapsid proteins and envelope proteins?
Which component of the virus serves to mediate interaction between nucleocapsid proteins and envelope proteins?
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What term describes the protein coat that protects a virus's genome?
What term describes the protein coat that protects a virus's genome?
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Which virus is known to produce superantigens causing non-specific activation of T cells?
Which virus is known to produce superantigens causing non-specific activation of T cells?
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What is a key characteristic of retroviruses in terms of genome structure?
What is a key characteristic of retroviruses in terms of genome structure?
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Which virus family is characterized by a non-segmented, positive polarity RNA structure and is known for causing hepatitis?
Which virus family is characterized by a non-segmented, positive polarity RNA structure and is known for causing hepatitis?
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What happens to viruses during the process of budding?
What happens to viruses during the process of budding?
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Which type of RNA virus is known to have a helical structure and includes the rabies virus?
Which type of RNA virus is known to have a helical structure and includes the rabies virus?
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Identify the virus family that has a circular, two-segmented RNA structure and is known to cause lymphocytic choriomeningitis.
Identify the virus family that has a circular, two-segmented RNA structure and is known to cause lymphocytic choriomeningitis.
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Which virus family includes the Ebola and Marburg viruses with a non-segmented, negative polarity RNA structure?
Which virus family includes the Ebola and Marburg viruses with a non-segmented, negative polarity RNA structure?
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Identify the medically important virus that is classified under the Picornavirus family.
Identify the medically important virus that is classified under the Picornavirus family.
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Which of the following virus families is associated with segmented RNA and has a negative polarity?
Which of the following virus families is associated with segmented RNA and has a negative polarity?
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Which family of viruses is characterized by having an envelope, icosahedral capsid symmetry, and a linear, positive polarity RNA structure?
Which family of viruses is characterized by having an envelope, icosahedral capsid symmetry, and a linear, positive polarity RNA structure?
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What type of virus structure is displayed by the Togavirus family, which includes the Rubella virus?
What type of virus structure is displayed by the Togavirus family, which includes the Rubella virus?
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Which virus family has a unique structure of single-stranded circular RNA with cohesive ends and is recognized for its pathogenicity?
Which virus family has a unique structure of single-stranded circular RNA with cohesive ends and is recognized for its pathogenicity?
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Which one of the following viruses is known to have an icosahedral structure with non-segmented, positive polarity RNA?
Which one of the following viruses is known to have an icosahedral structure with non-segmented, positive polarity RNA?
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Which DNA virus family is known to have no envelope and possesses a double-stranded, linear DNA structure?
Which DNA virus family is known to have no envelope and possesses a double-stranded, linear DNA structure?
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What describes the eclipse period in viral replication?
What describes the eclipse period in viral replication?
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Which of the following viruses is classified as a hepadnavirus?
Which of the following viruses is classified as a hepadnavirus?
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Which viral family is known for having a complex structure and possesses double-stranded, linear DNA?
Which viral family is known for having a complex structure and possesses double-stranded, linear DNA?
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Which of the following viruses has a single-stranded and linear DNA structure?
Which of the following viruses has a single-stranded and linear DNA structure?
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What is the defining characteristic of the herpesvirus family?
What is the defining characteristic of the herpesvirus family?
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In which viral family would you find JC virus and BK virus?
In which viral family would you find JC virus and BK virus?
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Which classification relates to the capsid symmetry of polyomaviruses?
Which classification relates to the capsid symmetry of polyomaviruses?
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Study Notes
RNA Virus Classification
- Picornaviruses are non-enveloped viruses with an icosahedral capsid symmetry. Their genome is single-stranded, linear, nonsegmented, and has positive polarity. Important examples include poliovirus, rhinovirus, and hepatitis A virus.
- Hepeviruses are also non-enveloped viruses with an icosahedral capsid symmetry. Their genome is single-stranded, linear, nonsegmented, and has positive polarity. Hepatitis E virus is the primary medical example.
- Caliciviruses are non-enveloped viruses with an icosahedral capsid symmetry. Their genome is single-stranded, linear, nonsegmented, and has positive polarity. Norwalk virus is a significant example.
- Reoviruses are non-enveloped viruses with an icosahedral capsid symmetry. Their genome is double-stranded, linear, segmented, and contains 10 or 11 segments. Rotavirus is a major example.
- Flaviviruses are enveloped viruses with an icosahedral capsid symmetry. Their genome is single-stranded, linear, nonsegmented, and has positive polarity. Important examples include yellow fever virus, dengue virus, West Nile virus, and hepatitis C virus.
- Togaviruses are enveloped viruses with icosahedral capsid symmetry and an RNA genome that is single-stranded, linear, nonsegmented, and has positive polarity. Rubella virus is the most notable example.
- Retroviruses are enveloped viruses with an icosahedral capsid symmetry. Their genome is single-stranded, linear, and contains two identical strands (diploid). The polarity is positive. HIV and human T-cell leukemia virus are prominent examples.
- Orthomyxoviruses are enveloped viruses with a helical capsid symmetry. Their genome is single-stranded, linear, segmented, and has negative polarity. Influenza virus is the primary example.
- Paramyxoviruses are enveloped viruses with a helical capsid symmetry. Their genome is single-stranded, linear, nonsegmented, and has negative polarity. Significant examples include measles virus, mumps virus, and respiratory syncytial virus.
- Rhabdoviruses are enveloped viruses with a helical capsid symmetry. Their genome is single-stranded, linear, nonsegmented, and has negative polarity. Rabies virus is the most notable example.
- Filoviruses are enveloped viruses with a helical capsid symmetry. Their genome is single-stranded, linear, nonsegmented, and has negative polarity. Ebola virus and Marburg virus are prominent examples.
- Coronaviruses are enveloped viruses with a helical capsid symmetry. Their genome is single-stranded, linear, nonsegmented, and has positive polarity.
- Arenaviruses are enveloped viruses with a helical capsid symmetry. Their genome is single-stranded, circular, segmented, and has negative polarity. The two segments are connected by cohesive ends. Lymphocytic choriomeningitis virus is a significant example.
- Bunyaviruses are enveloped viruses with a helical capsid symmetry. Their genome is single-stranded, circular, segmented, and has negative polarity. The three segments are connected by cohesive ends. California encephalitis virus and hantavirus are notable examples.
- Deltaviruses are enveloped viruses with an uncertain capsid symmetry. Their genome is single-stranded, circular, and has a closed circle, negative polarity. Hepatitis delta virus is the primary example.
Viral Replication
- All viruses have one copy of their genome (haploid), except for retroviruses, which have two copies (diploid).
- Viruses replicate by entering host cells and utilizing their machinery (e.g., ribosomes, enzymes) to synthesize new viral proteins and replicate their genetic material.
- This process can be divided into early events, late events, and assembly/release.
Virus Structure
- Capsid: A protein coat that protects the viral genome from nucleases. It is composed of repeating subunits called capsomers.
- Nucleocapsid: The capsid and the enclosed nucleic acid.
- Icosahedral Capsids: Capsomeres are arranged in 20 triangles, forming a symmetric figure (icosahedron). This structure appears as an approximate sphere. All DNA viruses are icosahedral except poxvirus, which has a complex capsid.
- Helical Capsids: Capsomeres are arranged in a hollow coil that appears rod-shaped.
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Viral Proteins:
- Surface proteins: Mediate attachment to host cell receptors and are targets of antibodies which inhibit viral replication.
- Internal proteins: Include DNA or RNA polymerases.
- Matrix protein: Connects the viral nucleocapsid and envelope proteins.
- Superantigens: Non-specific T-cell activators produced by some viruses like Epstein-Barr virus and Cytomegalovirus.
- Regulatory proteins: Control viral and cellular processes.
- Viral Envelope: Lipid bilayer containing viral glycoproteins and lipids derived from the host cell. The envelope is acquired as the virus buds off from the host cell.
Enveloped vs. Naked Viruses
- Enveloped Viruses: More sensitive to heat, drying, and disinfectants (alcohol, detergents) due to the presence of the lipid bilayer. Transmission typically occurs through blood and body fluids.
- Naked Viruses: More resistant to heat, drying, and disinfectants. Transmission often happens through indirect routes, like fecal-oral.
Viral Growth Curve
- Eclipse Period: The time during which no virus is found inside the cell. This ends with the appearance of new virus particles.
- Latent Period: The time from the onset of infection to the appearance of virus extracellularly.
- Viral Nucleic acid continues to function and begins to accumulate within the cell.
- Virus disappears and the virus particle is no longer detectable within the cell.
DNA Virus Classification
- Parvoviruses are non-enveloped viruses with an icosahedral capsid symmetry. Their genome is single-stranded, linear. B19 virus is a significant example.
- Polyomaviruses are non-enveloped viruses with an icosahedral capsid symmetry. Their genome is double-stranded, circular, supercoiled. Important examples include JC virus and BK virus.
- Papillomaviruses are non-enveloped viruses with an icosahedral capsid symmetry. Their genome is double-stranded, circular, supercoiled. Human papilloma virus is the primary example.
- Adenoviruses are non-enveloped viruses with an icosahedral capsid symmetry. Their genome is double-stranded, linear.
- Hepadnaviruses are enveloped viruses with an icosahedral capsid symmetry. Their genome is double-stranded, incomplete circular. Hepatitis B virus is the primary example.
- Herpesviruses are enveloped viruses with an icosahedral capsid symmetry. Their genome is double-stranded, linear. Herpes simplex virus, varicella-zoster virus, cytomegalovirus, and Epstein-Barr virus are notable examples.
- Poxviruses are enveloped viruses with complex capsid symmetry. Their genome is double-stranded, linear. Smallpox virus and molluscum contagiosum virus are prominent examples.
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Description
Test your knowledge on the classification of RNA viruses, including families like Picornaviruses, Hepeviruses, Caliciviruses, Reoviruses, and Flaviviruses. This quiz covers their structural features and key examples. Challenge yourself to see how well you understand these important pathogens.
