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Questions and Answers
Which viruses are human pathogens that belong to the category of coronaviruses?
Which viruses are human pathogens that belong to the category of coronaviruses?
What characteristic shape do rhabdoviruses have?
What characteristic shape do rhabdoviruses have?
Which disease is associated with the SARS-Cov virus family?
Which disease is associated with the SARS-Cov virus family?
What type of RNA do filoviruses contain?
What type of RNA do filoviruses contain?
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Which pathogen is primarily considered a rhabdovirus?
Which pathogen is primarily considered a rhabdovirus?
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Which of the following is NOT a human pathogen represented in the content?
Which of the following is NOT a human pathogen represented in the content?
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What was the approximate fatality rate of SARS during its outbreak?
What was the approximate fatality rate of SARS during its outbreak?
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What two primary components constitute a virus?
What two primary components constitute a virus?
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Which size range applies to most viruses compared to the cells they infect?
Which size range applies to most viruses compared to the cells they infect?
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What is the natural reservoir for the CoV-SARS?
What is the natural reservoir for the CoV-SARS?
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What is a complete virus particle called?
What is a complete virus particle called?
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Which characteristic is NOT used to classify virus families?
Which characteristic is NOT used to classify virus families?
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How do virions typically protect their genetic material?
How do virions typically protect their genetic material?
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What is the significance of a virus's size concerning filtration?
What is the significance of a virus's size concerning filtration?
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Which type of symmetry can a virus capsid exhibit?
Which type of symmetry can a virus capsid exhibit?
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What indicates the pathogenicity of a virus?
What indicates the pathogenicity of a virus?
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What type of genetic material do adenoviruses contain?
What type of genetic material do adenoviruses contain?
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Which family of viruses is known for causing latent infections?
Which family of viruses is known for causing latent infections?
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What characteristic distinguishes hepadnaviruses from other virus families?
What characteristic distinguishes hepadnaviruses from other virus families?
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Which virus is known to be used in the smallpox vaccine?
Which virus is known to be used in the smallpox vaccine?
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What is the diameter of picornaviruses?
What is the diameter of picornaviruses?
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Which of the following viruses can be classified as a member of the calicivirus family?
Which of the following viruses can be classified as a member of the calicivirus family?
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Which family of viruses is characterized by being the largest and having a complex capsid symmetry?
Which family of viruses is characterized by being the largest and having a complex capsid symmetry?
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What is unique about the DNA structure found in Hepadnaviruses?
What is unique about the DNA structure found in Hepadnaviruses?
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What forms the basis for division into genera and species within a virus family?
What forms the basis for division into genera and species within a virus family?
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Which type of viral genome cannot be directly used as a template for protein synthesis?
Which type of viral genome cannot be directly used as a template for protein synthesis?
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What type of symmetry characterizes the capsids of viruses with multiple different polypeptides?
What type of symmetry characterizes the capsids of viruses with multiple different polypeptides?
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In helical symmetry, what component is hydrogen-bonded to neighboring protomers?
In helical symmetry, what component is hydrogen-bonded to neighboring protomers?
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How is the nucleic acid genome positioned in an icosahedral capsid structure?
How is the nucleic acid genome positioned in an icosahedral capsid structure?
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What are the most common forms of viral genomes found in nature?
What are the most common forms of viral genomes found in nature?
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What is a significant characteristic of positive-strand RNA viruses?
What is a significant characteristic of positive-strand RNA viruses?
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What structural components do helical capsids rely on for their formation?
What structural components do helical capsids rely on for their formation?
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What is the primary mode of transmission for MERS coronavirus (MERS-CoV) to humans?
What is the primary mode of transmission for MERS coronavirus (MERS-CoV) to humans?
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In what year was COVID-19 first identified?
In what year was COVID-19 first identified?
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What percentage of people recovering from COVID-19 do not require special treatment?
What percentage of people recovering from COVID-19 do not require special treatment?
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Which virus strain causes COVID-19?
Which virus strain causes COVID-19?
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What is a common symptom of COVID-19?
What is a common symptom of COVID-19?
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According to the data, what is the incubation period for COVID-19?
According to the data, what is the incubation period for COVID-19?
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What proportion of COVID-19 patients may develop severe illness?
What proportion of COVID-19 patients may develop severe illness?
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Which of the following conditions increases the risk of developing serious illness from COVID-19?
Which of the following conditions increases the risk of developing serious illness from COVID-19?
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Which of the following vaccines utilizes mRNA technology?
Which of the following vaccines utilizes mRNA technology?
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What type of virus is the Johnson & Johnson vaccine based on?
What type of virus is the Johnson & Johnson vaccine based on?
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Which type of RNA virus has double-stranded RNA as part of its structure?
Which type of RNA virus has double-stranded RNA as part of its structure?
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Which viral family contains single-stranded DNA viruses?
Which viral family contains single-stranded DNA viruses?
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What classification system is primarily used to categorize viruses?
What classification system is primarily used to categorize viruses?
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Which vaccine is categorized as a protein-based vaccine?
Which vaccine is categorized as a protein-based vaccine?
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Which of the following RNA viruses have positive-polarity RNA?
Which of the following RNA viruses have positive-polarity RNA?
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Which type of viruses are classified as naked nucleocapsid viruses?
Which type of viruses are classified as naked nucleocapsid viruses?
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Study Notes
Medical Important Viruses
- Viruses are infectious agents,
- Constructed of two components:
- A genome (RNA or DNA, but not both)
- A protein-containing structure (capsid) to protect the genome.
- Some viruses have an additional lipid-containing envelope.
- A complete virus particle is a virion.
- Viruses replicate inside host cells.
- Viral replication is a process that is obligately intracellular.
Virus Structure
- Viruses are much smaller than cells (100-1000 times smaller).
- Smallest viruses are 20nm in diameter, while the largest are ~300nm.
- Viruses can pass through filters that trap bacteria.
Virus Classification
- Viruses are categorized into families, subfamilies, genera, and species.
- Classification is based on several factors: genome type and structure, replication strategy, capsid shape (helical or icosahedral), and presence or absence of lipid envelope.
Viral Genomes
- Viral genomes can be DNA or RNA, either single-stranded (ss) or double-stranded (ds).
- Common forms in nature are ssRNA and dsDNA.
- Single-stranded RNA genomes are further classified based on polarity
- Positive-polarity RNA genomes are similar in sequence to mRNA, and can be directly used as templates for protein synthesis.
- Negative-polarity RNA genomes are complementary to mRNA, and need to be transcribed into positive-polarity RNA before being translated into proteins.
Viral Capsid Symmetry
- Most virus capsids are either helical or icosahedral in shape.
- Helical capsids are rod-shaped or coiled.
- Icosahedral capsids are spherical or symmetric.
- Capsids are constructed from multiple copies of a single or several polypeptide subtypes.
Viral Envelopes
- Some viruses have an envelope, a lipid membrane surrounding the nucleocapsid.
- Envelopes are derived from the host cell membrane.
- Enveloped viruses are generally more sensitive to environmental factors than non-enveloped viruses.
Viral Replication
- Viruses replicate using a series of steps, beginning with attachment to a host cell, followed by penetration and uncoating of the viral genome.
- Gene expression and replication occur, with the assembly of viral progeny, and finally, release of viral progeny from the cell.
Baltimore Classification
- Viruses are classified into seven groups based on their genome characteristics.
- I: dsDNA
- II: ssDNA
- III: dsRNA
- IV: (+)ssRNA
- V: (−)ssRNA
- VI: (+)-ssRNA-RT
- VII: dsDNA-RT
Types of DNA Viruses
- Naked icosahedral: parvoviruses, papovaviruses, and adenoviruses are examples of naked icosahedral DNA viruses.
- Enveloped icosahedral: hepadnaviruses, and herpesviruses are examples of enveloped icosahedral DNA viruses.
- Largest DNA viruses: Poxviruses: have complex internal symmetry
Types of RNA Viruses
- Based on symmetry, some are enveloped and some naked.
- Picornaviruses, caliciviruses, and reoviruses are RNA viruses without an envelope.
- Reoviruses have double-stranded RNA; other RNA viruses have single-stranded RNA.
- Reoviruses and influenza viruses have segmented RNA; the others have non-segmented RNA.
- Picornaviruses, caliciviruses, flaviviruses, togaviruses, retroviruses, and coronaviruses have positive-polarity RNA, while others have negative-polarity RNA.
Other Important Viral Groups
- Coronavirus
- Togavirus
- Retrovirus
- Orthomyxovirus
- Paramyxovirus
- Rhabdovirus
- Filovirus
Disease information
- Viruses can cause various diseases, including the common cold, pneumonia, and other respiratory illnesses.
- Specific viruses can cause diseases like SARS, MERS, and COVID-19.
- Modes of transmission (airborne, direct contact, fecal-oral) differ among viruses.
Prevention, Treatment and Control
- Prevention strategies (hand hygiene, vaccination) are important to contain virus spread.
- Molecular tests (nucleic acid detection, serology) are used in diagnosing viral infections.
- Vaccination is important for preventive measures.
- Variants of viruses, notably SARS-CoV-2, can emerge over time, potentially with altered transmissibility and disease severity.
References
- Various books on microbiology and virology, as listed in the supplementary slides.
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Description
This quiz delves into the essential aspects of medical viruses, including their structure, classification, and replication mechanisms. Learn about the fundamental components of viruses and how they interact with host cells. Test your knowledge on viral genomes and the size comparison with bacteria.
