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Questions and Answers
What is the main human pathogen associated with reoviruses?
What is the main human pathogen associated with reoviruses?
Which group of viruses includes the rubella virus?
Which group of viruses includes the rubella virus?
What type of genetic material do flaviviruses possess?
What type of genetic material do flaviviruses possess?
Which virus is classified as an orthomyxovirus?
Which virus is classified as an orthomyxovirus?
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What is a characteristic feature of retroviruses?
What is a characteristic feature of retroviruses?
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Which of the following viruses is part of the flavivirus family?
Which of the following viruses is part of the flavivirus family?
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What is the primary distinguishing feature of enveloped viruses?
What is the primary distinguishing feature of enveloped viruses?
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Which of the following viruses is classified as a ssRNA virus?
Which of the following viruses is classified as a ssRNA virus?
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What type of RNA segments do orthomyxoviruses typically have?
What type of RNA segments do orthomyxoviruses typically have?
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What defines a naked virus?
What defines a naked virus?
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Which viruses are classified as lentiviruses?
Which viruses are classified as lentiviruses?
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Which of the following is NOT an example of an enveloped virus?
Which of the following is NOT an example of an enveloped virus?
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Papovaviruses are characterized by which type of genetic material?
Papovaviruses are characterized by which type of genetic material?
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Which classification group includes the rabies virus?
Which classification group includes the rabies virus?
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What type of symmetry do poxviruses exhibit?
What type of symmetry do poxviruses exhibit?
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How does the envelope of an enveloped virus originate?
How does the envelope of an enveloped virus originate?
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What is the mode of transmission of MERS to humans?
What is the mode of transmission of MERS to humans?
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What virus strain causes COVID-19?
What virus strain causes COVID-19?
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Which symptom is NOT commonly associated with COVID-19?
Which symptom is NOT commonly associated with COVID-19?
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What percentage of people with COVID-19 become seriously ill?
What percentage of people with COVID-19 become seriously ill?
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What are the two main components that make up a virus?
What are the two main components that make up a virus?
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When did the WHO declare COVID-19 a pandemic?
When did the WHO declare COVID-19 a pandemic?
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What is a virion?
What is a virion?
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What is the typical incubation period for COVID-19?
What is the typical incubation period for COVID-19?
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Which factor does NOT contribute to the pathogenicity of a virus?
Which factor does NOT contribute to the pathogenicity of a virus?
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Which group is more likely to develop serious illness from COVID-19?
Which group is more likely to develop serious illness from COVID-19?
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Which of the following is a common symptom of MERS?
Which of the following is a common symptom of MERS?
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How small are viruses compared to the cells they infect?
How small are viruses compared to the cells they infect?
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What property allows viruses to pass through filters designed to trap bacteria?
What property allows viruses to pass through filters designed to trap bacteria?
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Which characteristic is NOT used to define virus families and species?
Which characteristic is NOT used to define virus families and species?
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What is the role of the capsid in a virus?
What is the role of the capsid in a virus?
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Which characteristic distinguishes between different virus groups?
Which characteristic distinguishes between different virus groups?
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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 virus is primarily associated with the Hepadnaviruses family?
Which virus is primarily associated with the Hepadnaviruses family?
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Herpesviruses are known for causing which type of infections?
Herpesviruses are known for causing which type of infections?
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What is a distinguishing feature of poxviruses?
What is a distinguishing feature of poxviruses?
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Which characteristic is true about Picornaviruses?
Which characteristic is true about Picornaviruses?
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Caliciviruses have which of the following characteristics?
Caliciviruses have which of the following characteristics?
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What common infections do adenoviruses typically cause?
What common infections do adenoviruses typically cause?
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What is a unique feature of the genetic structure of Hepadnaviruses?
What is a unique feature of the genetic structure of Hepadnaviruses?
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What type of viral genome can be classified as positive polarity?
What type of viral genome can be classified as positive polarity?
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Which of the following describes capsids with helical symmetry?
Which of the following describes capsids with helical symmetry?
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How do icosahedral capsids differ from helical capsids?
How do icosahedral capsids differ from helical capsids?
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What is the role of hydrogen bonding in viral capsid structures?
What is the role of hydrogen bonding in viral capsid structures?
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What is the primary characteristic of negative-strand RNA viruses?
What is the primary characteristic of negative-strand RNA viruses?
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Which component is formed when protomers and nucleic acid associate in helical capsids?
Which component is formed when protomers and nucleic acid associate in helical capsids?
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Which of the following statements about viral genomes is true?
Which of the following statements about viral genomes is true?
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What defines the classification of viruses into genera and species?
What defines the classification of viruses into genera and species?
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Study Notes
Medical Important Viruses
- Viruses are infectious agents composed of two components: a nucleic acid (either RNA or DNA, but not both) and a protein-containing structure (capsid).
- The capsid protects the genome.
- Many viruses have additional features, like an envelope made from a lipid bilayer with protein.
- A complete virus particle is called a virion.
- Viruses replicate inside host cells.
- Viruses replicate intracellularly.
- Pathogenicity of a virus depends on structural and functional characteristics.
- Different species of viruses may cause significantly different clinical pathologies, even within similar groups of viruses.
- Viruses are much smaller than cells, typically 100-1000 times smaller.
- Viruses range in diameter from 20nm (parvoviruses) to 300nm (poxviruses).
- Viruses can pass through filters that block bacteria, which can be used as evidence of a viral etiology.
Virus Structure
- Viruses are broadly classified into families, genera, and species based on different characteristics.
- Viral classification includes the type and structure of viral nucleic acid.
- Viral classification also looks at replication strategies, capsid symmetry (helical or icosahedral), and the presence/absence of a lipid envelope.
- Viruses vary in shape based on capsid symmetry (spherical or rod-shaped), which involves different numbers of structural components.
Virus Genome
- Viral genomes can be DNA or RNA, single or double-stranded.
- Single-stranded RNA (ssRNA) viruses are frequently further subdivided into positive or negative polarity, based on whether they can be directly used as mRNA for protein synthesis.
Virus Capsid Symmetry
- The capsid, the protein shell surrounding the genome, can be either helical or icosahedral, depending on the virus.
- It's built of multiple copies of a single polypeptide, or a few in the case of icosahedral capsids.
Viral Symmetry (Helical)
- Helical symmetry is a cylindrical or rod-shaped arrangement of proteins.
- Identical proteins interact repeatedly along the length.
- The nucleic acid is also helical.
Viral Symmetry (Icosahedral)
- Icosahedral symmetry refers to the spherical or quasi-spherical shape.
- The capsid is made of multiple copies of a few proteins.
- The arrangements of proteins form a 20-sided structure, with identical or similar proteins forming a repeating pattern.
Viral Envelope
- Some viruses have an envelope, a membrane-forming outer layer.
- Envelopes are derived from the host cell membrane but are coated in virus-specific proteins.
- Enveloped viruses are often more fragile.
- Non-enveloped viruses are sometimes referred to as naked viruses.
Viral Replication
- The replication cycle involves several stages, beginning with attachment to host cells, penetration, and uncoating of the genome.
- This is followed by viral gene expression and genome replication, viral assembly, and release of new virions to continue the cycle.
- Several key steps or genes influence the replication cycle.
Viral Classification
- Baltimore classification groups viruses into families based on their specific genetic characteristics, including their single vs double-stranded and RNA vs DNA nature.
- Seven groups are recognized.
DNA Viruses
- Naked and enveloped viruses with differing characteristics, including the type of internal structure or features.
RNA Viruses
- Naked or enveloped icosahedral viruses with different shapes and external characteristics.
- Classified by RNA strands, and the existence of segments in the RNA genome.
Poxviruses
- These are among the largest viruses, with unusual morphology and complex internal structures.
Herpesviruses
- These enveloped viruses typically cause latent infections, and some are associated with specific human diseases.
Parvoviruses
- Naked icosahedral viruses with DNA genomes and small particle sizes.
Adenoviruses
- Naked icosahedral viruses with DNA genomes, typically causing mild respiratory tract diseases.
Hepadnaviruses
- Enveloped icosahedral viruses with unusual DNA genomes with partially missing single strands.
Picornaviruses
- Small, non-enveloped positive-sense RNA viruses, with various human pathogens as examples.
Caliciviruses
- Small, non-enveloped, positive-sense RNA viruses involved in viral gastroenteritis and related diseases.
Reoviruses
- Naked, icosahedral viruses with segmented, double-stranded RNA genomes.
Flaviviruses
- Enveloped positive-sense RNA viruses involved with human diseases like hepatitis C, dengue fever, West Nile virus, etc.
Togaviruses
- Enveloped, positive-sense RNA viruses causing diseases ranging from western equine encephalitis to rubella/measles.
Retroviruses
- Enveloped RNA viruses that use reverse transcriptase to convert their RNA genome into DNA.
Orthomyxoviruses
- Enveloped viruses, including influenza virus, with segmental negative-sense RNA genomes.
Paramyxoviruses
- Enveloped viruses including measles, mumps, parainfluenza, with segmental, negative-sense RNA genomes.
Rhabdoviruses
- Enveloped bullet-shaped viruses with negative-sense RNA, like rabies virus.
Filoviruses
- Enveloped viruses that are long, filamentous structures with negative-sense RNA inside.
Coronaviruses
- Enveloped single-stranded RNA viruses, often causing respiratory illnesses.
Diseases Caused by Viruses
- SARS (2002) emerged as an atypical pneumonia, caused by SARS-CoV.
- MERS (2012) emerged as a severe pneumonia, caused by MERS-CoV.
- COVID-19 (2019), caused by SARS-CoV-2.
Covid-19 Symptoms
- The most common symptoms of COVID-19 are fever, tiredness, and dry cough, often mild and gradual.
- Some patients may have other symptoms, including aches, pains, nasal congestion, runny nose, sore throat, or diarrhea.
Covid-19 Prevention
- Several preventive measures are available, including handwashing, avoiding contact with infected individuals, wearing masks, and avoiding crowded places.
COVID-19 Vaccines
- Different types of vaccines are available, including mRNA, inactivated virus, and viral vector types.
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Description
This quiz explores the fundamental characteristics of important viruses, including their structure, replication, and pathogenicity. Gain insights into how viruses operate at a cellular level and their classification within the viral families and species. Perfect for students in medical or biological sciences.
