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Questions and Answers
What is the final step in the assembly process of enveloped viruses?
What is the final step in the assembly process of enveloped viruses?
Which of the following viruses is known to be non-cytopathic and associated with persistent infections?
Which of the following viruses is known to be non-cytopathic and associated with persistent infections?
Where do flaviviruses acquire their envelopes during assembly?
Where do flaviviruses acquire their envelopes during assembly?
How do herpesviruses release virions from the cell?
How do herpesviruses release virions from the cell?
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What type of genetic material do rhabdoviruses possess?
What type of genetic material do rhabdoviruses possess?
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What occurs when a fluid sample containing a virus is placed in a well of agar opposite a well containing antiserum?
What occurs when a fluid sample containing a virus is placed in a well of agar opposite a well containing antiserum?
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Which virus families are primarily associated with the hemagglutination phenomenon?
Which virus families are primarily associated with the hemagglutination phenomenon?
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What is the primary purpose of the polymerase chain reaction (PCR)?
What is the primary purpose of the polymerase chain reaction (PCR)?
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Which of the following is NOT a method of diagnostic serology?
Which of the following is NOT a method of diagnostic serology?
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What term describes the binding of erythrocytes to cells infected with hemagglutinating viruses?
What term describes the binding of erythrocytes to cells infected with hemagglutinating viruses?
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What is a virion?
What is a virion?
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What characterizes the capsid of vertebrate viruses?
What characterizes the capsid of vertebrate viruses?
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Which type of capsid symmetry is NOT mentioned?
Which type of capsid symmetry is NOT mentioned?
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What role do glycoproteins play in viral envelopes?
What role do glycoproteins play in viral envelopes?
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Which statement best describes capsomeres?
Which statement best describes capsomeres?
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What is a key factor during the attachment phase of viral replication?
What is a key factor during the attachment phase of viral replication?
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What is the primary environment where viruses replicate?
What is the primary environment where viruses replicate?
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How long can the duration of a viral replication cycle range?
How long can the duration of a viral replication cycle range?
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What role does viral neuraminidase play in some viruses?
What role does viral neuraminidase play in some viruses?
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What is the energy dependency of virus uptake into a host cell?
What is the energy dependency of virus uptake into a host cell?
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During which process is the viral genome released for transcription?
During which process is the viral genome released for transcription?
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Where does the synthesis of viral mRNA typically occur for DNA viruses that replicate in the nucleus?
Where does the synthesis of viral mRNA typically occur for DNA viruses that replicate in the nucleus?
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Which proteins are synthesized on membrane-bound ribosomes?
Which proteins are synthesized on membrane-bound ribosomes?
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What happens during the post-translational modification of viral proteins?
What happens during the post-translational modification of viral proteins?
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How are non-enveloped viruses typically released from the host cell?
How are non-enveloped viruses typically released from the host cell?
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Where does assembly occur for Picornaviruses and Reoviruses?
Where does assembly occur for Picornaviruses and Reoviruses?
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How do enveloped viruses such as poxviruses release their virions?
How do enveloped viruses such as poxviruses release their virions?
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What is a key characteristic of the assembly and release process of poxviruses?
What is a key characteristic of the assembly and release process of poxviruses?
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Which sample collection method is suitable for diagnosing respiratory viral diseases?
Which sample collection method is suitable for diagnosing respiratory viral diseases?
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What is the purpose of the buffered isotonic saline with bovine albumin in sample transport?
What is the purpose of the buffered isotonic saline with bovine albumin in sample transport?
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What is a limitation of using electron microscopy for virus detection?
What is a limitation of using electron microscopy for virus detection?
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What laboratory technique can be used to demonstrate the presence of viral antigens in specimens?
What laboratory technique can be used to demonstrate the presence of viral antigens in specimens?
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Why is it critical to collect samples for virus isolation and send them without delay?
Why is it critical to collect samples for virus isolation and send them without delay?
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What is usually required before a virus becomes adapted to a particular cell line in culture?
What is usually required before a virus becomes adapted to a particular cell line in culture?
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Study Notes
Introduction to Viruses (Part 2)
- This presentation discusses viruses and their components, structure, and replication process.
Virion Structure
- A virion is a fully assembled infectious virus.
- The fundamental component is a nucleoprotein core with the ability to infect and replicate within host cells, ensuring continued survival.
- A virion possesses a lipid envelope that is composed of a lipid bilayer plus associated glycoproteins.
Capsid
- The capsid is a protein shell that encloses the genome of vertebrate viruses.
- The nucleocapsid describes the packaged form of the genome in the capsid.
- Two types of capsid symmetry:
- Icosahedral symmetry
- Helical symmetry
Viral Structure
- Viruses have a capsid (protein sheath), a DNA/RNA genome, and an envelope (protein).
- Bacteriophage, Tobacco mosaic virus (TMV), and Human immunodeficiency virus (HIV) are examples of viruses.
Envelope
- In many viruses, the nucleocapsid is covered by an envelope comprised of a lipid bilayer and associated glycoproteins.
- The glycoproteins are essential for binding host cell receptors, membrane fusion, uncoating of the virion, and destruction of receptors on host cells.
- The envelope is acquired when the nucleocapsid buds through the cellular membrane.
Epitopes
- Epitopes on envelope glycoproteins are vital for inducing protective immune responses in infected animals.
Baltimore Classifications
- Classify viruses based on genome nature and mRNA synthesis pathways.
- There are 7/6 classes.
Virus Replication Stages
- Attachment to receptor on host cell
- Entry into the host cell (endocytosis or membrane fusion)
- Uncoating (release of viral genome)
- Replication of viral nucleic acid and protein synthesis
- Assembly of new virions
- Release from host cell (budding or cell lysis)
Attachment
- Virus-cell interaction is crucial for host range and tissue tropism.
- Some viruses use multiple ligands to bind several cell surface receptors.
- Virion detachment and re-adsorption to different cells occurs in some viruses, often mediated by viral neuraminidase enzyme (that destroys receptors on cells).
Entry into the Cell
- Virus uptake/penetration is an energy-dependent process.
- Mechanisms include receptor-mediated endocytosis and fusion of viral envelope with the plasma membrane.
Uncoating
- The process where the viral genome is released in a form suitable for transcription.
- Enveloped viruses commonly shed nucleocapsid directly into the cytoplasm, skipping complete uncoating.
- Nuclei-replicating viruses may uncoat within the nuclear pore complex.
Synthesis of Viral Proteins
- Viral protein synthesis is essential for virus replication.
- DNA viruses often leverage host cell transcriptases for mRNA synthesis.
- The synthesis is driven by the viral genome.
- Some viruses produce their own specific enzymes for mRNA synthesis.
Protein Synthesis
- Membrane proteins and glycoproteins are synthesized by membrane-bound ribosomes.
- Other soluble proteins, like enzymes, are produced by cytoplasm-free ribosomes.
- Post-translational modifications are also critical (cleaving, phosphorylation, and glycosylation).
Assembly of Virions
- Assembled virions differentiate in their structure.
- Non-enveloped viruses typically have an icosahedral structure.
- Assemble at the periphery of the cell.
- Budding is associated with release in enveloped viruses.
- Viral assembly locations vary depending on the virus (e.g cytoplasm for some, nucleus for others).
Release of Virions
- Release type varies based on viral structure (enveloped vs. non-enveloped).
- Enveloped viruses release new virions via budding. Non-enveloped viruses frequently release viruses after the cell disintegrates.
- Cell lysis is associated with release from some viruses, budding from others.
Laboratory Diagnosis of Viral Infections
- Diagnostics often are based on clinical signs, post-mortem findings, and histopathological changes from infected tissues.
- Proper sample collection method is crucial for analysis, followed by appropriate techniques (e.g., cell culture, electron microscopy, immunoassay, PCR, etc.).
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Description
This quiz delves into the intricacies of viruses, focusing on their structure, components, and replication processes. Learn about the virion structure, capsid types, and envelopes of different viruses through targeted questions.
