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Questions and Answers
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?
Which of the following describes the most common forms of viral genomes found in nature?
Which of the following describes the most common forms of viral genomes found in nature?
What is the primary construction unit of helical capsids?
What is the primary construction unit of helical capsids?
What characterizes positive-strand RNA viruses?
What characterizes positive-strand RNA viruses?
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What is the role of capsomers in icosahedral symmetry?
What is the role of capsomers in icosahedral symmetry?
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How are nucleic acids organized within icosahedral capsids?
How are nucleic acids organized within icosahedral capsids?
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What is a defining feature of viruses with helical symmetry?
What is a defining feature of viruses with helical symmetry?
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What distinguishes negative-strand RNA viruses from positive-strand RNA viruses?
What distinguishes negative-strand RNA viruses from positive-strand RNA viruses?
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Which virus is classified under the hepevirus genus?
Which virus is classified under the hepevirus genus?
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What type of nucleic acid do reoviruses possess?
What type of nucleic acid do reoviruses possess?
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Which virus is a major human pathogen among the flaviviruses?
Which virus is a major human pathogen among the flaviviruses?
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What is the primary human pathogen associated with retroviruses?
What is the primary human pathogen associated with retroviruses?
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What is the primary structural feature that distinguishes enveloped viruses from naked viruses?
What is the primary structural feature that distinguishes enveloped viruses from naked viruses?
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In the context of viral classification, which group includes viruses such as herpes and adeno?
In the context of viral classification, which group includes viruses such as herpes and adeno?
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Which viruses fall under the category of paramyxoviruses?
Which viruses fall under the category of paramyxoviruses?
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Which of the following best describes the human papillomavirus?
Which of the following best describes the human papillomavirus?
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Which viruses are classified as enveloped viruses with an icosahedral capsid and nonsegmented, positive-polarity RNA?
Which viruses are classified as enveloped viruses with an icosahedral capsid and nonsegmented, positive-polarity RNA?
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What is the significance of the name 'retroviruses'?
What is the significance of the name 'retroviruses'?
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Which of the following viruses is classified under the (-)ssRNA group?
Which of the following viruses is classified under the (-)ssRNA group?
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What identifies the main human pathogen within the orthomyxoviruses?
What identifies the main human pathogen within the orthomyxoviruses?
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What occurs immediately after a virus attaches to a host cell during its replication cycle?
What occurs immediately after a virus attaches to a host cell during its replication cycle?
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What are the characteristics of poxviruses?
What are the characteristics of poxviruses?
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What is the size range of parvoviruses within their respective family?
What is the size range of parvoviruses within their respective family?
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Which of the following is true about the proteins found in the envelope of enveloped viruses?
Which of the following is true about the proteins found in the envelope of enveloped viruses?
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Which platform does the Pfizer-BioNTech COVID-19 vaccine belong to?
Which platform does the Pfizer-BioNTech COVID-19 vaccine belong to?
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What type of virus is the Sputnik vaccine classified as?
What type of virus is the Sputnik vaccine classified as?
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Which of the following vaccines is based on an inactivated virus?
Which of the following vaccines is based on an inactivated virus?
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What type of genome does parvovirus contain?
What type of genome does parvovirus contain?
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Which of the following is NOT a characteristic of reoviruses?
Which of the following is NOT a characteristic of reoviruses?
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What classification do herpesviruses belong to based on their genome?
What classification do herpesviruses belong to based on their genome?
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Which family of viruses is known to have positive-polarity RNA?
Which family of viruses is known to have positive-polarity RNA?
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Which type of nucleic acid is primarily found in adenoviruses?
Which type of nucleic acid is primarily found in adenoviruses?
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What is the primary mode of transmission of MERS to humans?
What is the primary mode of transmission of MERS to humans?
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What strain of coronavirus causes COVID-19?
What strain of coronavirus causes COVID-19?
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What percentage of people infected with COVID-19 typically recover without special treatment?
What percentage of people infected with COVID-19 typically recover without special treatment?
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What is the length of the incubation period for COVID-19?
What is the length of the incubation period for COVID-19?
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Which of the following is NOT a common symptom of COVID-19?
Which of the following is NOT a common symptom of COVID-19?
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Who is more likely to develop serious illness from COVID-19?
Who is more likely to develop serious illness from COVID-19?
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When did WHO declare COVID-19 a pandemic?
When did WHO declare COVID-19 a pandemic?
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What animal is thought to be a reservoir for the MERS coronavirus?
What animal is thought to be a reservoir for the MERS coronavirus?
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Which virus is the only significant human pathogen among rhabdoviruses?
Which virus is the only significant human pathogen among rhabdoviruses?
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What is the primary cause of respiratory tract infections linked to coronaviruses?
What is the primary cause of respiratory tract infections linked to coronaviruses?
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What is the mean diameter of filoviruses?
What is the mean diameter of filoviruses?
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What does the term 'rhabdo' refer to in the context of rhabdoviruses?
What does the term 'rhabdo' refer to in the context of rhabdoviruses?
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Which of the following viruses is associated with the disease COVID-19?
Which of the following viruses is associated with the disease COVID-19?
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What fatality rate was associated with the SARS outbreak in 2002?
What fatality rate was associated with the SARS outbreak in 2002?
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Which animal is identified as the natural reservoir for the SARS coronavirus?
Which animal is identified as the natural reservoir for the SARS coronavirus?
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Which two viruses are classified as human pathogens in the filovirus family?
Which two viruses are classified as human pathogens in the filovirus family?
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Study Notes
Medical Important Viruses
- Viruses are infectious agents constructed of nucleic acid (RNA or DNA) and a protein coat (capsid).
- Many viruses have additional features like an envelope made of lipid and protein.
- A complete virus particle is called a virion.
- Viruses reproduce within host cells.
- Viral pathogenicity depends on structural and functional characteristics.
- Different viral species can have significantly distinct clinical effects.
Virus Structure
- Viruses are much smaller than cells, typically 100-1000 times smaller.
- Parvoviruses are the smallest, while poxviruses are the largest.
- Viruses can pass through filters designed to trap bacteria.
Virus Classification
- Viruses are grouped into families, subfamilies, genera, and species.
- Key characteristics used for classification include viral nucleic acid type, replication strategy, capsid symmetry (helical or icosahedral), and presence/absence of an envelope.
Viral Genome
- Viral genomes can be DNA or RNA, either single-stranded (ss) or double-stranded (ds).
- The most common genomes found in nature are ssRNA and dsDNA.
- Viral RNA genomes are subdivided into positive-polarity (used for protein synthesis) and negative-polarity (not used directly for protein synthesis) types.
Capsid Symmetry
- The protein shell enclosing the viral genome (capsid) has two geometric forms: helical or icosahedral.
- The capsid is made of repeating copies of one or a few protein subunits.
- Different viruses have different numbers and types of proteins in their capsids.
- Genetic information is limited to what it takes to code for the structural components.
Envelopes
- Some viruses have envelopes derived from the host cell membrane.
- Viral proteins are integrated into the envelope.
- The presence or absence of an envelope is a characteristic used to classify viruses.
Viral Replication
- Viral replication involves attachment, penetration, uncoating, gene expression, replication, assembly, and release.
Baltimore Classification
- The Baltimore classification system groups viruses based on the mechanism used to generate mRNA.
- There are seven groups including those with dsDNA, ssDNA, dsRNA, (+)ssRNA, (-)ssRNA, (+)ssRNA-RT, and dsDNA-RT types of viruses.
DNA Viruses
- There are three primary naked (nonenveloped) icosahedral families (parvoviruses, papovaviruses, adenoviruses).
- Hepadnaviruses and herpesviruses are enveloped icosahedral viruses.
- Poxviruses have a complex internal symmetry.
Papovaviruses
- Naked icosahedral viruses with double-stranded circular DNA.
- Three human papovaviruses (Human papillomavirus; BK virus; JC virus).
Adenoviruses
- Naked icosahedral viruses with double-stranded linear DNA.
- Cause mild diseases like pharyngitis.
Hepadnaviruses
- Double-shelled viruses with an icosahedral capsid covered by an envelope.
- Hepatitis B virus is the most significant pathogen.
Herpesviruses
- Enveloped viruses with icosahedral nucleocapsids and double-stranded linear DNA.
- Cause latent infections.
- Examples are herpes simplex virus types 1 and 2, varicella-zoster virus, cytomegalovirus, and Epstein-Barr virus.
Poxviruses
- The largest viruses.
- Brick-like shape with an envelope.
- Examples include smallpox and vaccinia viruses.
RNA Viruses
- Naked icosahedral viruses without an envelope.
- Reoviruses have double-stranded RNA, while other RNA viruses have single-stranded RNA and can categorized into segmented and non-segmented RNA families.
- Positive-polarity and negative-polarity types of viruses exist for RNA viruses.
Picornaviruses
- Smallest RNA viruses, naked icosahedral type.
- Cause a variety of diseases including polio, coxsackievirus, echovirus, hepatitis A and rhinoviruses.
Caliciviruses
- Naked icosahedral viruses.
- Cause diarrhea and have single-stranded positive-polarity RNA.
- Hepatitis E virus is the significant pathogen.
Reoviruses
- Naked viruses with two icosahedral capsid coats.
- Have double-stranded linear RNA.
- Rotavirus is the most significant pathogen.
Flaviviruses
- Enveloped viruses with icosahedral capsids and single-stranded linear RNA.
- Significant pathogens are hepatitis C virus, yellow fever virus, dengue virus, West Nile virus, and St. Louis and Japanese encephalitis viruses.
Togaviruses
- Enveloped viruses with icosahedral capsids and positive-polarity, single-stranded, linear RNA.
- Alphaviruses (eastern and western encephalitis viruses) and rubiviruses (rubella virus).
Retroviruses
- Enveloped viruses with a helical nucleocapsid and diploid single-stranded linear positive-polarity RNA.
- Replication involves reverse transcription of RNA to DNA.
- Human pathogens are sarcoma and leukemia viruses, Human T-cell leukemia virus, and HIV.
Orthomyxoviruses
- Enveloped viruses with helical nucleocapsids and single-stranded, non-segmented, negative-polarity RNA.
- Examples are influenza viruses.
Paramyxoviruses
- Enveloped viruses with helical nucleocapsid and single-stranded, non-segmented, negative-polarity RNA.
- Measles, mumps, parainfluenza, and respiratory syncytial viruses.
Rhabdoviruses
- Bullet-shaped enveloped viruses with helical nucleocapsid and single-stranded, non-segmented, negative-polarity RNA.
- Examples include rabies virus.
Filoviruses
- Enveloped viruses with helical nucleocapsid and single-stranded, non-segmented, negative-polarity RNA.
- Ebola virus and Marburg virus are significant pathogens.
Coronaviruses
- Enveloped viruses with helical nucleocapsids and single-stranded, non-segmented, positive-polarity RNA.
- Common cold, SARS, MERS, and COVID-19 are related diseases.
Virus Diseases
- Many viruses cause disease in humans.
- Various types of viral diseases impact people across the globe.
Methods for diagnosing viral infections
- Nucleic acid detection through PCR tests.
- Antibody tests through blood samples.
COVID-19 Vaccines
- Several vaccines for COVID-19 have been developed and deployed
- These vaccines use different underlying approaches and platforms including mRNA, inactivated virus, and viral vector.
COVID-19 Prevention, Transmission, and Symptoms
- Wash hands frequently.
- Avoid close contact with infected individuals.
- Wear a mask.
- Avoid crowded areas that could create a conducive environment for spreading.
- Common symptoms are fever, tiredness, dry cough, aches, pains, nasal congestion, runny nose, sore throat or diarrhea.
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Description
This quiz explores key concepts about viruses, including their structure, classification, and pathogenicity. Examine the features that distinguish different viral species and their effects on host organisms. Test your knowledge on viral genomes and their characteristics.
