Virology Quiz: Virus Classification and Characteristics

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Questions and Answers

What type of DNA do adenoviruses have?

Double-stranded circular DNA

Single-stranded circular DNA

Double-stranded linear DNA (correct)

Single-stranded linear DNA

Which virus is a member of the hepadnavirus family?

Rhinovirus

Echovirus

Hepatitis B virus (correct)

Herpes simplex virus

What is a notable characteristic of herpesviruses?

They cause latent infections. (correct)

They contain only single-stranded RNA.

They are the smallest viruses.

They are naked and cause skin lesions.

What is the shape of poxviruses?

Bricklike (B) Signup and view all the answers

What do picornaviruses contain within their capsid?

Single-stranded positive-polarity RNA (B) Signup and view all the answers

Which of the following is NOT a human pathogen of herpesviruses?

Rhinovirus (A) Signup and view all the answers

What type of RNA do caliciviruses have?

Single-stranded linear RNA (B) Signup and view all the answers

Which family do adenoviruses belong to?

DNA viruses (C) Signup and view all the answers

What are the two main components that make up a virus?

RNA or DNA and a capsid (D) Signup and view all the answers

What is referred to as a complete virus particle?

Virion (A) Signup and view all the answers

Which characteristic is NOT used to classify viruses into families?

Size of the virus (A) Signup and view all the answers

What is the significance of a virus’s lipid envelope?

It acts as a protective barrier against host immune responses. (D) Signup and view all the answers

Why are viruses typically smaller than the cells they infect?

All of the above. (D) Signup and view all the answers

What is the typical size range of viruses compared to bacteria?

100- to 1000-fold smaller than bacteria (A) Signup and view all the answers

What does the term 'pathogenicity' of a virus depend on?

A variety of structural and functional characteristics (A) Signup and view all the answers

Which statement accurately describes a virus's genome?

It may include enzymes for replication. (D) Signup and view all the answers

What is the main criterion for dividing viruses into genera and species?

Differences in specific properties such as host range and amino acid sequences (C) Signup and view all the answers

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

Negative-strand RNA (A) Signup and view all the answers

What geometric configurations do the protein shells of most virus families typically exhibit?

Helical or icosahedral (A) Signup and view all the answers

What term describes the complex of protomers and nucleic acid in helical capsids?

Nucleocapsid (C) Signup and view all the answers

How are capsomers in icosahedral symmetry structured?

They are hydrogen-bonded groups of different polypeptides (C) Signup and view all the answers

What does a capsid with helical symmetry typically consist of?

A single type of polypeptide species (A) Signup and view all the answers

What type of viral genome is considered a template for protein synthesis?

Positive-strand RNA (C) Signup and view all the answers

What is the role of the capsid in a virus?

Protect the viral genetic material and aid in its delivery into host cells (D) Signup and view all the answers

What virus is categorized under the hepevirus genus?

Hepatitis E virus (C) Signup and view all the answers

Which virus is primarily responsible for diarrhea in infants?

Rotavirus (D) Signup and view all the answers

What type of RNA do flaviviruses possess?

Single-stranded linear RNA (B) Signup and view all the answers

Which group of viruses includes the rubella virus?

Togaviruses (B) Signup and view all the answers

What characterizes retroviruses in terms of their RNA structure?

Diploid single-stranded RNA (B) Signup and view all the answers

Which virus primarily causes influenza?

Influenza virus (D) Signup and view all the answers

How many segments of RNA do orthomyxoviruses have?

Eight segments of linear RNA (D) Signup and view all the answers

Which category of viruses includes the human immunodeficiency virus (HIV)?

Retroviruses (A) Signup and view all the answers

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

Close contact with camels (C) Signup and view all the answers

What is the incubation period for COVID-19?

1-14 days (C) Signup and view all the answers

What percentage of individuals infected with COVID-19 typically recover without special treatment?

80% (A) Signup and view all the answers

Which underlying health issue increases the risk of serious illness from COVID-19?

High blood pressure (B) Signup and view all the answers

What symptom is NOT commonly associated with COVID-19?

Loss of appetite (B) Signup and view all the answers

What is the name of the virus responsible for causing MERS?

MERS-CoV (A) Signup and view all the answers

When did WHO declare COVID-19 a pandemic?

March 2020 (A) Signup and view all the answers

What symptom typically indicates severe illness in COVID-19 patients?

Difficulty breathing (B) Signup and view all the answers

What is the primary structural difference between enveloped and naked viruses?

Naked viruses lack a lipid-containing membrane. (A) Signup and view all the answers

Which of the following is NOT a classification group of viruses based on their genetic material?

polyDNA (D) Signup and view all the answers

In which viral family would you find the Hepatitis B virus?

Hepadnaviruses (A) Signup and view all the answers

What defines the envelope of an enveloped virus?

It is derived from the host cell membrane. (D) Signup and view all the answers

Which of the following viruses is classified as a naked icosahedral virus?

Adenovirus (A) Signup and view all the answers

What is the size of papovaviruses compared to other naked icosahedral viruses?

They are of medium size within the group. (A) Signup and view all the answers

What occurs immediately after virus attachment during the replication cycle?

Penetration of the viral genome takes place. (A) Signup and view all the answers

Which of the following viruses is specifically a human papovavirus?

BK virus (C) Signup and view all the answers

Study Notes

Medical Important Viruses

Viruses are infectious agents with a minimal structure
They consist of a genome (RNA or DNA, not both), and a protein-containing structure (capsid) that protects the genome
Some viruses have additional features, such as a lipid-containing membrane (envelope)
A complete virus particle is called a virion
Viruses reproduce inside host cells
Viruses can be in a variety of shapes and sizes, and the shape and size features are used to distinguish the types
Viruses are classified into families, genera, and species based on characteristics like the type and structure of the viral nucleic acid, replication strategies, type of capsid symmetry (helical or icosahedral), and the presence/absence of a lipid envelope
Viruses are much smaller than cells
The size of viruses ranges from 20 nm in diameter for the smallest viruses (parvoviruses) to 300 nm for the largest (poxviruses)
A complete virus particle is called a virion
Viruses require host cells for replication
Viral pathogenicity depends on many structural and functional characteristics
Different viruses from one species can have very different clinical pathologies

Virus Structure

Viruses are significantly smaller than cells
Viruses are 100-1000 fold smaller than the cells they infect
Virus sizes are similar to the size of bacteria

Viral Replication

Virus replication involves steps like attachment, penetration, uncoating, gene expression, replication, assembly, and release of viral progeny

Icosahedral Symmetry

Icosahedral symmetry is described as a complex structure that has numerous faces and thus is spherical or symmetrical
Viral capsids are formed from subunits called capsomers, which are arranged in an icosahedral pattern
Viral genomes found within this structure

Helical Symmetry

Helical symmetry refers to a rod or coil shape (symmetric)
The capsid is constructed of a single polypeptide that forms a helical structure around the nucleic acid to form the shape
The complex of protomers and nucleic acid is called the nucleocapsid

Enveloped Viruses

Enveloped viruses have a lipid-containing outer layer (envelope) surrounding their nucleocapsid
Enveloped viruses are derived from host cell membranes and replaced by virus-specific proteins
Envelope proteins confer virus-specific antigenicity
Enveloped viruses are more sensitive to environmental conditions compared to naked viruses
The size and shape are characteristic of enveloped shapes
Naked viruses do not have these membranes; thus, they are not as sensitive to environmental changes

Baltimore Classification System

This is used to classify viruses based on their genome structure and the form of mRNA they make
The system classifies viruses into 7 groups; I (dsDNA), II (ssDNA), III (dsRNA), IV (+ssRNA), V (-ssRNA), VI (+ssRNA-RT), & VII (dsDNA-RT)

DNA Viruses

These viruses have DNA genomes
These are naked viruses with an icosahedral capsid; thus, they are non-enveloped
The size increases in order-parvoviruses, papovaviruses, and adenoviruses
There are enveloped viral families such as hepadnaviruses and herpesviruses
The poxviruses are the largest and have complex internal symmetry

Papovaviruses

These viruses are non-enveloped and circular DNA
These viruses include papilloma, polyoma, and simian vacuolating viruses
Usually cause cancer

Adenoviruses

These viruses are non-enveloped
Icosahedral symmetrical viruses with a double-stranded linear DNA
Mostly cause mild diseases, including nose, mouth, and throat infections
There are more than 40 subtypes

Hepadnaviruses

Enveloped viruses with an icosahedral capsid
Have a partially double-stranded DNA genome
Characterized by reverse transcription
Hepatitis B is a human pathogen from this family

Herpesviruses

These viruses are enveloped with a double-stranded linear DNA
Usually noted for causing latent infections (indefinite period of virus replication)
Hepatitis B causes diseases like chicken pox and infectious mononucleosis, among others
There are 5 important human pathogens—herpes simplex viruses (HSV types 1 & 2), varicella-zoster virus, cytomegalovirus, Epstein-Barr virus

Poxviruses

These are the largest viruses and have a complex capsid
Possess a bricklike shape, and their envelopes have unique appearances
Most are characterized by skin lesions or "pocks"
Smallpox virus and vaccinia virus are important members

RNA Viruses

These viruses have an RNA genome and are classified into 8 families depending on their structures, presence or absence of an envelope, and type of polarity
Coronaviruses, retroviruses, flaviviruses, reoviruses, togaviruses, Orthomyxoviruses, bunyaviruses, and paramyxoviruses are enveloped RNA viruses with single-stranded RNA with (+) or (-) polarity
Naked RNA viruses include picornaviruses, caliciviruses, and reoviruses

Picornaviruses

These are the smallest RNA viruses with (+) polarity
These are non-enveloped with an icosahedral capsid
Human pathogens like poliovirus, coxsackievirus, rhinovirus, and hepatitis A virus are included
The size varies

Caliciviruses

Naked RNA viruses with an icosahedral capsid and (+) polarity
They cause diarrhea
Human pathogens are noroviruses and sapoviruses

Reoviruses

Naked RNA viruses with 2 icosahedral capsids; thus, they are non-enveloped
Double-stranded RNA; thus, they have 10 segments
Rotavirus is the main human pathogen and causes diarrhea mostly in infants

Flaviviruses

Enveloped RNA viruses with (+) polarity and an icosahedral capsid
Include dengue virus, yellow fever virus, West Nile virus, and Japanese encephalitis virus

Togaviruses

Enveloped RNA viruses with (+) polarity and an icosahedral capsid
Include alphaviruses (Eastern and Western encephalitis viruses) and rubella virus

Retroviruses

Enveloped RNA viruses with (+) polarity and an icosahedral capsid
Include human immunodeficiency virus (HIV) and human T-cell leukemia/lymphoma virus (HTLV)

Paramyxoviruses

Enveloped RNA viruses with (-) polarity and a helical nucleocapsid
Include measles, mumps, parainfluenza viruses, and respiratory syncytial viruses

Rhabdoviruses

Enveloped RNA viruses with (-) polarity, helical nucleocapsid
Include rabies virus

Filoviruses

Enveloped RNA viruses with (-) polarity, helical nucleocapsid
Ebola and Marburg viruses are included here

Coronaviruses

Enveloped RNA viruses with (+) polarity, helical nucleocapsid
Have a halo of spikes protruding from the envelope
Include SARS-CoV, MERS-CoV, and SARS-CoV-2

Viral Diseases

Important human viruses, including those classified as DNA viruses and RNA viruses, cause several diseases. Viral infections can affect various systems in the human body.

Molecular Tests for Virus Detection

Nucleic acid detection tests are used to detect viral RNA or DNA (SARS-COV-2) in infected people

Antibody Tests for Virus Exposure

These tests (serology) are used to detect an immune response against the virus—indicates previous exposure to a virus (SARS-COV-2)

COVID-19 Vaccines

Several platforms exist, including mRNA, inactivated viral vectors, protein-based

Prevention, Symptoms, and Severity of COVID-19

Prevention involves handwashing, avoiding contact with sick people, wearing masks, and avoiding crowded places
Symptoms include fever, tiredness, cough, aches, nasal congestion, runny nose, sore throat, and diarrhea
Severe symptoms include difficulty breathing and high blood pressure

SARS-CoV-2 Variants

Different viral variants caused by mutations in the virus's genetic material have been labelled

References

Information from the slides provides the references

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Description

Test your knowledge on viruses, including their classification, characteristics, and components. This quiz covers various virus families, structures, and significant features, providing a comprehensive overview of virology concepts. Ideal for students and enthusiasts of microbiology and virology.