Virology Quiz on Viruses and Their Characteristics

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Questions and Answers

What is the primary characteristic that differentiates enveloped viruses from naked viruses?

Size of the virus

Lipid-containing membrane surrounding the nucleocapsid (correct)

Presence of a rigid structure

Absence of genetic material

Which of the following viruses is classified as a dsRNA virus?

Hepadnavirus

Papillomavirus

HIV

Reovirus (correct)

Which of the following correctly describes papovaviruses?

RNA viruses that require reverse transcription

Enveloped viruses with single-stranded RNA

Large complex viruses with segmented genomes

Naked icosahedral viruses with double-stranded circular DNA (correct)

Which of the following is NOT a feature of enveloped viruses?

Presence of host cell membrane proteins Signup and view all the answers

What is the approximate size of papovaviruses?

55 nm Signup and view all the answers

Which virus family includes the hepatitis B virus?

Hepadnavirus Signup and view all the answers

What is the main function of the viral envelope?

Confer antigenicity and facilitate attachment to host cells Signup and view all the answers

How are cellular membrane proteins handled in enveloped viruses?

They are replaced by virus-specific proteins Signup and view all the answers

Which genus has hepatitis E virus been placed into?

Hepevirus Signup and view all the answers

What type of RNA do reoviruses have?

Double-stranded, linear RNA Signup and view all the answers

Which of the following viruses is NOT classified as a flavivirus?

Rotavirus Signup and view all the answers

Which group of viruses includes the rubella virus?

Togaviruses Signup and view all the answers

What is the main human pathogen associated with orthomyxoviruses?

Influenza virus Signup and view all the answers

Which characteristic is true for retroviruses?

They utilize reverse transcription Signup and view all the answers

Which viruses are classified with negative-polarity RNA?

Paramyxoviruses Signup and view all the answers

What is a major human pathogen of the reovirus family?

Rotavirus Signup and view all the answers

Which type of vaccine uses the mRNA platform?

Moderna’s COVID-19 vaccine Signup and view all the answers

Which viral classification describes viruses that have an envelope?

RNA viruses with an envelope Signup and view all the answers

What is the key characteristic of parvoviruses?

Single-stranded DNA Signup and view all the answers

Which vaccine is based on the use of an inactivated virus?

Sinovac vaccine Signup and view all the answers

Which type of RNA do reoviruses contain?

Double-stranded RNA Signup and view all the answers

What distinguishes viral vectors from other vaccine platforms?

They deliver a genetic code using another virus Signup and view all the answers

Which of the following is not a type of positive-polarity RNA virus?

Influenza viruses Signup and view all the answers

Which vaccine is classified as protein-based?

Novavax vaccine Signup and view all the answers

What is the primary mode of transmission of MERS to humans?

Close contact with camels Signup and view all the answers

What was the significant outcome of the World Health Organization (WHO) declaration on March 11, 2020?

COVID-19 was declared a pandemic Signup and view all the answers

Which of the following is NOT a common symptom of COVID-19?

Flu-like symptoms Signup and view all the answers

What percentage of people who contract COVID-19 become seriously ill and develop difficulty breathing?

16% Signup and view all the answers

What is the incubation period for COVID-19?

1-14 days Signup and view all the answers

What virus strain is responsible for COVID-19?

SARS-CoV-2 Signup and view all the answers

Who is more likely to develop serious illness from COVID-19?

Older adults and those with underlying health conditions Signup and view all the answers

What is another name for the MERS coronavirus?

HCoV-EMC Signup and view all the answers

Which virus is the only important human pathogen in the Rhabdovirus family?

Rabies virus Signup and view all the answers

Which viruses are known to cause severe pneumonia besides COVID-19?

MERS and SARS Signup and view all the answers

What does the term 'corona' refer to in Coronaviruses?

The halo of spikes protruding from the envelope Signup and view all the answers

Which of the following is NOT classified as a Filovirus pathogen?

Rabies virus Signup and view all the answers

What is the most likely natural reservoir for the CoV-SARS virus?

Horseshoe bat Signup and view all the answers

When did the outbreak of SARS first emerge?

2002 Signup and view all the answers

Which of the following coronaviruses emerged in 2020?

SARS-Cov-2 Signup and view all the answers

What is the common characteristic of viruses in the Rhabdoviruses family?

Bullet shape with a single-stranded linear negative-polarity RNA Signup and view all the answers

What forms the basis for division into genera and species within a virus family?

Differences in specific properties such as host range and serologic reactions Signup and view all the answers

Which of the following describes the most common forms of viral genomes found in nature?

Single-stranded RNA and double-stranded DNA Signup and view all the answers

What structural configuration does a helical symmetric capsid most commonly take?

A coiled cylindrical shape formed by a single polypeptide Signup and view all the answers

How are capsomers in icosahedral symmetric capsids bonded?

Through hydrogen bonds to form a rigid structure Signup and view all the answers

What type of RNA genome cannot be used directly as a template for protein synthesis?

Negative-strand RNA Signup and view all the answers

In what structural aspect do helical capsids differ from icosahedral capsids?

Helical capsids consist of a single polypeptide type, while icosahedral capsids use multiple polypeptides Signup and view all the answers

What is created by hydrogen-bonded protomers and nucleic acid in a helical capsid?

Nucleocapsid Signup and view all the answers

Why is it significant that some viral RNA genomes are classified as positive polarity?

They can be directly used as a template for protein synthesis Signup and view all the answers

Study Notes

Medical Important Viruses

Viruses are infectious agents made of a genome (RNA or DNA, not both) and a protein-containing structure (capsid) to protect the genome.
Some viruses have an additional lipid-containing envelope.
A complete virus particle is called a virion, which acts like a delivery system for the genome.
Viruses need a host cell to replicate, and the method of replication is intracellular.
Viral pathogenicity depends on structural and functional characteristics, even within related virus groups.

Virus Structure

Viruses are much smaller than cells (100-1000 times smaller).
The smallest viruses are ~20nm in diameter, while the largest are ~300nm.
This small size allows viruses to pass through filters designed to trap bacteria.

Viral Structure

Viruses have a protein shell (capsid) which encloses the genome.
The capsid may be helical (rod-shaped) or icosahedral (spherical).
The capsid is composed of multiple copies of a single protein(or a few proteins), requiring limited genetic information.

Viral Genome

Viral genomes may be RNA or DNA, either single-stranded (ss) or double-stranded (ds).
ssRNA can be positive-polarity (messenger RNA sense) or negative-polarity (antisense).
ssRNA viruses are most common.
Positive-sense RNA can immediately be used as a template for protein synthesis, while negative-sense needs to be converted first.

Viral Capsid Symmetry

The capsid, the protein shell encloses the genome.
Viruses can be helical (rod-shaped) or icosahedral (spherical or symmetrical).
The capsid is formed from multiple copies of a single polypeptide or a few different polypeptides.

Helical Symmetry

Capsids with helical symmetry are similar to a cylinder, composed of repeating units of the same polypeptide. These units are bound together with hydrogen bonds.

Icosahedral Symmetry

Icosahedral symmetry capsids are more complex.
They are composed of multiple different polypeptide units called capsomers that arrange in an icosahedron shape.

Viral Envelope

Some viruses have an envelope, a lipid-containing membrane acquired from the host cell.
The envelope contains proteins that help the virus bind to host cells.
Viruses without envelopes are called "naked" viruses.

Viral Replication

The replication cycle begins with virus attachment to a host cell and leads to penetration and uncoating of the viral genome.
Gene expression and replication follow uncoating, then assembly and release of viral progeny.

Baltimore Classification

Viruses are classified into seven groups based on their genome structure and viral replication.
- dsDNA viruses (herpes, adeno, pox, papova)
- ssDNA viruses (parvo)
- dsRNA viruses (reo, rota)
- (+)ssRNA viruses (picorna, toga, flavi, corona)
- (-)ssRNA viruses (rhabdo, orthomyxo, bunya, filo)
- (+)ssRNA-RT viruses (retro, lenti)
- dsDNA-RT viruses (hepadna)

Papoviruses

Papovaviruses are nonenveloped, icosahedral viruses containing double-stranded circular DNA.
They can cause different diseases in humans.

Adenoviruses

Adenoviruses are nonenveloped, icosahedral viruses with double stranded linear DNA.
They can cause various diseases in humans.

Hepadnaviruses

Hepadnaviruses are enveloped viruses that appear roughly spherical and have a double shelled capsid with double-stranded DNA but a missing strand.
Hepatitis B virus is a human pathogen in this family.

Herpesviruses

Herpesviruses are enveloped with an icosahedral nucleocapsid and double-stranded linear DNA.
They can cause latent infections.

Poxviruses

Poxviruses are the largest viruses with a brick-like shape, an envelop, and have a complex capsid symmetry.
They are responsible for skin lesions ("pocks.")

RNA Viruses

RNA viruses are categorized into eight groups based on their properties.

Picornaviruses

Picornaviruses are small, naked viruses with single-stranded RNA.
They can cause various diseases in humans.

Caliciviruses

Caliciviruses are naked viruses with single-stranded RNA and have an icosahedral capsid shape.
Some can cause diarrhea.

Reoviruses

Reoviruses are naked viruses with two icosahedral capsids and double-stranded RNA segments.
Rotavirus causes diarrhea, mainly in infants.

Flaviviruses

Flaviviruses are enveloped viruses with a single-stranded RNA and an icosahedral capsid.
They cause yellow fever, dengue fever, West Nile virus, and Japanese encephalitis.

Togaviruses

Togaviruses are enveloped viruses with a single-stranded RNA.
Western and Eastern encephalitis are examples caused by these viruses

Retroviruses

Retroviruses are enveloped viruses with single-stranded RNA.
They contain the enzyme reverse transcriptase that transcribes RNA into DNA.

Paramyxoviruses

Paramyxoviruses are enveloped viruses containing eight segments of single-stranded, negative-sense RNA in their helical nucleocapsid.
They contain human Measles, Mumps, Parainfluenza, and Respiratory Syncytial viruses.

Rhabdoviruses

Rhabdoviruses are enveloped viruses with a helical nucleocapsid and a single-stranded RNA.
The only important human pathogen is Rabies virus.

Filoviruses

Filoviruses are enveloped viruses with a helical nucleocapsid and a single-stranded RNA.
Ebola virus and Marburg virus are the important human pathogens.

Coronaviruses

Coronaviruses are enveloped viruses with a helical nucleocapsid and single-stranded RNA, and prominent spike proteins.
Common cold, SARS, MERS and COVID-19 are diseases caused by these viruses

Medical Important Viruses Diseases

Different types of coronaviruses are viruses can cause the common cold, SARS, MERS, and COVID-19.

COVID-19 Symptoms

Common symptoms of COVID-19 include fever, tiredness, dry cough, aches, pains, nasal congestion, runny nose, sore throat, and diarrhea.
Severe symptoms include difficulty breathing and high blood pressure.

Covid-19 Prevention

Wash hands often, maintain physical distance, and wear a mask to help slow the spread of COVID-19.

Molecular Tests for COVID-19

Nucleic acid detection tests use PCR to detect viral RNA in samples.
Antibody tests detect the presence of antibodies to SARS-CoV-2.

COVID-19 Vaccines

Several COVID-19 vaccines are available worldwide inactivated virus, mRNA, viral vector, and protein-based vaccines.

Virus Variants

New labels and classification for SARS-CoV-2 variants based on their origin location are being assigned regularly.

Summary

Viruses are primarily classified based on their DNA/RNA type and if the virus has an envelope.
The summary emphasizes different RNA and DNA virus classifications, and examples.

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Description

Test your knowledge on various types of viruses, including their classifications, characteristics, and significant examples. This quiz covers enveloped and naked viruses, RNA types, and specific virus families, providing a comprehensive assessment of your virology understanding.