Features of Viruses Quiz

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Questions and Answers

What are the two types of nucleic acid that a virus can possess?

Both DNA and RNA

Only RNA

Either DNA or RNA, but not both (correct)

Only DNA

Which structural feature is common to all viruses?

A double-stranded RNA genome

A protein shell called a capsid (correct)

An external membrane envelope

A specific shape defined by symmetry

What does viral tropism refer to?

The ability of a virus to infect a variety of host cells

The specific cells or tissues a virus can infect (correct)

The diversity of viruses based on their structure

The method by which viruses replicate within a host

Which statement correctly describes viral persistence?

It refers to viruses that can lie dormant in non-infectious forms Signup and view all the answers

What is the role of the capsid in a virus?

To enclose the viral nucleic acid Signup and view all the answers

Which statement accurately reflects the mutation rates in RNA viruses compared to DNA viruses?

RNA viruses usually show much higher mutation rates than DNA viruses. Signup and view all the answers

Which mechanism is NOT involved in the penetration of a virus into a host cell?

Reverse transcription Signup and view all the answers

What term describes a virus's ability to infect a specific type of cell or tissue?

Viral tropism Signup and view all the answers

Which of the following viruses is categorized as a retrovirus?

HIV Signup and view all the answers

Which of the following is NOT considered a step in the viral life cycle?

Replication of host DNA Signup and view all the answers

What process allows a virus to attach firmly to a host cell?

Adsorption Signup and view all the answers

Which virus is commonly associated with the disease caused by varicella zoster?

Chickenpox Signup and view all the answers

Which statement correctly describes the eclipse period in viral infections?

Both A and C are correct. Signup and view all the answers

What happens during the eclipse phase of viral infection?

The virus cannot be detected and is non-infective. Signup and view all the answers

What role does mRNA play in viral replication?

It codes for the synthesis of enzymes needed for early replication. Signup and view all the answers

Which of the following viruses is known for causing persistent infections?

HIV Signup and view all the answers

What is a key characteristic of viral latency?

The virus enters a dormant state within the host cell. Signup and view all the answers

During viral assembly, nucleic acids are incorporated into what structure?

Capsomeres Signup and view all the answers

Which type of viral replication results in the host cell's death?

Lytic replication Signup and view all the answers

What characterizes persistent viral infections?

The virus remains in specific cells without causing immediate damage. Signup and view all the answers

Viral proteins can be classified into which of the following types?

Structural and non-structural proteins Signup and view all the answers

Study Notes

Features of a Virus

Viruses are infectious particles that reproduce by utilizing a host cell's machinery to create more viruses.
Composed of a DNA or RNA genome encased in a protein shell called a capsid.
Some viruses possess an external membrane envelope.
Viruses come in various shapes, structures, genomes, and infect different hosts.
Viruses reproduce by infecting host cells and reprogramming them to become virus-producing factories.

Genome

The genetic material of a virus, containing instructions for its replication.
Can be either DNA or RNA, but never both.

Capsid

The protein coat surrounding the virus's genome.
Provides protection and helps the virus attach to host cells.

Envelope

An outer membrane that surrounds some viruses.
Acquired from the host cell during viral release.
Contains viral proteins that aid in attachment and entry into new host cells.

Enzymes

Proteins that catalyze specific biochemical reactions within the virus.
Important for viral replication and spread.

Further Facts

Small size: 10-100 nanometers (nm), about 1/10 the size of bacteria.
Genome: RNA or DNA, never both.
Obligate intracellular parasites: Viruses can only multiply inside a living host cell.

Classification of Viruses

Symmetry:
- Icosahedral: 20 triangular faces, spherical appearance.
- Filamentous: Long, cylindrical shape.
- Head-tail: Complex structure with a head containing DNA and a tail for attachment.
Nucleic acid:
- DNA or RNA
- Viruses can have any combination of strandedness (single or double-stranded) and nucleic acid type (DNA or RNA).
- RNA viruses typically exhibit higher mutation rates than DNA viruses.

Common Viruses Relevant to Dentistry

Human Immunodeficiency Virus (HIV):
- Causes Acquired Immunodeficiency Syndrome (AIDS).
- Weakens the immune system, making individuals susceptible to infections.
Hepatitis B Virus:
- Causes inflammation of the liver.
- Can lead to chronic hepatitis, cirrhosis, and liver cancer.
Varicella Zoster Virus:
- Causes chickenpox in children and shingles in adults.
- A common viral rash.
Herpes Simplex Virus (HSV):
- Causes oral herpes (cold sores) and genital herpes.
Influenza Virus:
- Causes the flu.
- Characterized by respiratory symptoms like fever, cough, and sore throat.

Viral Tropism

The ability of a virus to infect a specific cell, tissue, or host species.
Determined by the virus's ability to attach to and enter specific host cells.

Viral Replication and Dissemination

Adsorption: Attachment of the virus particle to specific receptors on the host cell's surface.
Penetration: Entry of the virus or its genome into the host cell. This can occur by endocytosis, fusion, or translocation.
Uncoating/Eclipse: Removal of the viral envelope and capsid to release the nucleic acid.
Transcription: Synthesis of viral mRNA from the viral genome.
Synthesis of viral components: Production of viral proteins and nucleic acids using the host cell's machinery.
Assembly: The process of assembling new viral particles from the synthesized components.
Release: Release of new viral particles from the host cell. This can occur through lysis (killing the host cell) or budding (exiting without killing the host cell).

Viral Terms

Viral persistence: Long-term infection where the virus is not eliminated but remains in specific cells.
Viral latency: A stage where the virus remains dormant within a cell, not actively replicating.

Examples of Persistent Infections

HIV
Epstein-Barr Virus
Human Cytomegalovirus
Human Herpesviruses 6 and 7
Varicella-Zoster Virus
Human Papovaviruses
Hepatitis B Virus

Examples of Latent Infections

Herpes simplex virus (HSV)
Epstein-Barr virus (EBV)
Varicella-zoster virus (VZV)
Human immunodeficiency virus (HIV)

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Description

Test your knowledge on the characteristics and components of viruses. This quiz covers essential concepts such as viral structures, genomes, capsids, and envelopes. Understand how viruses reproduce and interact with host cells.