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Questions and Answers
What are the two types of nucleic acid that a virus can possess?
Which structural feature is common to all viruses?
What does viral tropism refer to?
Which statement correctly describes viral persistence?
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What is the role of the capsid in a virus?
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Which statement accurately reflects the mutation rates in RNA viruses compared to DNA viruses?
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Which mechanism is NOT involved in the penetration of a virus into a host cell?
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What term describes a virus's ability to infect a specific type of cell or tissue?
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Which of the following viruses is categorized as a retrovirus?
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Which of the following is NOT considered a step in the viral life cycle?
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What process allows a virus to attach firmly to a host cell?
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Which virus is commonly associated with the disease caused by varicella zoster?
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Which statement correctly describes the eclipse period in viral infections?
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What happens during the eclipse phase of viral infection?
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What role does mRNA play in viral replication?
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Which of the following viruses is known for causing persistent infections?
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What is a key characteristic of viral latency?
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During viral assembly, nucleic acids are incorporated into what structure?
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Which type of viral replication results in the host cell's death?
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What characterizes persistent viral infections?
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Viral proteins can be classified into which of the following types?
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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
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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.
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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.
