Viral Replication Process
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Questions and Answers

What is a key reason why viruses replicate?

  • To eliminate other pathogens in the host
  • To increase in numbers to overwhelm its host (correct)
  • To enhance host immune responses
  • To divide and create new cells

Which step is NOT part of the viral replication cycle?

  • Release of virus
  • Maturation
  • Cellular division (correct)
  • Assembly of virus

What is defined as the specific invasion and replication of a virus in a particular cell type?

  • Viral fusion
  • Tropism (correct)
  • Cellular immunology
  • Cytophagy

What is the role of cellular receptors in viral infections?

<p>To facilitate attachment and entry of the virus (C)</p> Signup and view all the answers

What type of cells does the Epstein-Barr virus primarily target?

<p>B cells (B)</p> Signup and view all the answers

Which stage of viral replication involves the virus shedding its protein coat?

<p>Uncoating (C)</p> Signup and view all the answers

Which type of tropism refers to a virus's ability to infect various host species?

<p>Broad tropism (B)</p> Signup and view all the answers

What is the first step in the viral replication cycle?

<p>Attachment (A)</p> Signup and view all the answers

What process is required for viral penetration into a host cell?

<p>Energy-dependent process (A)</p> Signup and view all the answers

How do enveloped viruses generally enter host cells?

<p>By fusing with the plasma membrane (A)</p> Signup and view all the answers

What triggers the fusion of certain enveloped viruses with endosomes?

<p>Acidification of endosome (D)</p> Signup and view all the answers

What does uncoating refer to in the viral life cycle?

<p>Removal or degradation of the viral capsid (B)</p> Signup and view all the answers

Which type of viral genome is associated with Retroviruses?

<p>ssRNA with DNA intermediate (C)</p> Signup and view all the answers

What is synthesized during the genome replication of a virus?

<p>Viral structural proteins (D)</p> Signup and view all the answers

Non-enveloped viruses can enter host cells by which method?

<p>Either crossing the membrane directly or being taken up into endosomes (B)</p> Signup and view all the answers

What happens after the viral genome is uncoated within the host cell?

<p>Viral replication and protein production can begin (B)</p> Signup and view all the answers

What is the main role of the capsid in a virus?

<p>To protect the viral nucleic acid (C)</p> Signup and view all the answers

What typically happens during the maturation stage of a virus?

<p>Viruses become infectious through structural changes (C)</p> Signup and view all the answers

How do newly formed viruses usually release from non-enveloped viruses?

<p>By cell lysis (D)</p> Signup and view all the answers

In which life cycle does the virus integrate into the host chromosomal DNA?

<p>Lysogenic cycle (A)</p> Signup and view all the answers

What outcome does the lytic cycle have on the infected cell?

<p>Destroys the cell (D)</p> Signup and view all the answers

Which type of virus release may or may not result in the death of the host cell?

<p>Release by budding (C)</p> Signup and view all the answers

Which structure forms during the assembly of viruses and is crucial for protecting viral nucleic acids?

<p>Capsid (B)</p> Signup and view all the answers

What type of virus typically undergoes a lytic cycle?

<p>Bacteriophage (B)</p> Signup and view all the answers

Flashcards

Viral Replication

The process where viruses multiply by assembling viral components into new virions, requiring a host cell.

Viral Tropism

The preference of a virus to infect specific types of cells.

Viral Replication Steps (Simple)

Attachment, Entry, Uncoating, Replication, Assembly, Maturation, Release

Viral Attachment

The virus binds to specific receptors on the host cell's surface.

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Viral Receptor

The specific molecules on the surface of cells that viruses recognize and bind to.

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Host Range

The range of host species and cells a virus can infect.

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Species Tropism

The invasion and replication of a virus in a specific cell type within a species.

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Why Viruses Replicate

To produce more virions and cause viral infection.

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Viral Penetration

The process where a virus enters a host cell. This can occur through endocytosis, translocation, or fusion with the cell membrane.

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Endocytosis for Viral Entry

A method of viral penetration where the host cell engulfs the virus, bringing it inside in a vesicle.

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Fusion for Viral Entry (Enveloped Viruses)

The viral envelope directly merges with the host cell membrane, releasing the viral contents inside.

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Acidification and Endosome Fusion

Some viruses require an acidic environment to fuse. They are taken into endosomes, which acidify, triggering fusion.

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Uncoating

After entry, the virus removes or degrades its protective coat, releasing its genetic material inside the host cell.

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Viral Replication: Genome Replication and Protein Production

The virus uses the host cell machinery to make copies of its own genetic material and proteins.

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Viral DNA Replication

The process of making more copies of the viral DNA within the host cell.

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Viral Assembly

New viral particles are assembled inside the host cell from the newly made viral components.

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What is a capsid?

A protein shell that encloses the viral nucleic acid, formed by hundreds to thousands of proteins.

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Where does viral assembly occur?

Viral assembly often takes place in modified areas of the cytoplasm called 'factories' or 'virosomes'. For some viruses, like adenoviruses, it happens in the nucleus.

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Virus Maturation

The stage where the newly assembled virus particle becomes infectious. This involves structural, chemical, and physical changes.

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How are enveloped viruses released?

Enveloped viruses are released by budding, where they pinch off from the host cell membrane, taking a piece of it with them.

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Release of non-enveloped viruses

Non-enveloped viruses are usually released by cell lysis, which leads to the death of the host cell.

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Lytic Cycle

The viral reproductive cycle where the virus quickly replicates, destroys the host cell, and releases many new viruses. This cycle involves the production of viruses utilizing the host cell's resources.

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Lysogenic Cycle

The viral reproductive cycle where the virus integrates its DNA into the host cell's DNA, becoming part of it. This state is called a prophage. The virus replicates with the host cell without killing it.

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What is a prophage?

The viral DNA integrated into the host cell's DNA during the lysogenic cycle.

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Study Notes

Viral Replication

  • Viral replication is a complex process; viruses do not replicate by division
  • Viruses assemble components into a complete virion
  • Essential for viral replication is a host cell, human, animal, or plant
  • A single virus particle does not cause disease; widespread infection and replication of numerous virus particles disrupt the host's function
  • Understanding viral replication helps to identify targets for antiviral strategies and prevention

Steps in Viral Replication

  • Attachment: Specific binding between virus and host cell receptors.
  • Penetration: Entry of the virus into the host cell (endocytosis, fusion, translocation)
  • Uncoating: Release of the viral genome from the capsid.
  • Genome Replication: Viral genetic material is replicated.
  • Assembly: Viral structural proteins assemble with the genome to form new virions
  • Maturation: The newly formed virions become infectious
  • Release: The new virions leave the host cell, by budding or lysis

Viral Tropism

  • Viruses do not infect all cells.
  • Viruses have evolved to infect specific cells or tissues
  • Virus-host cell interactions are specific to each viral species
  • Viral tropism is the virus's invasion and replication of a certain cell type

Examples of Viral Target Cells

  • HIV: Helper T cells
  • Epstein-Barr virus: B cells
  • Poliovirus: Epithelial cells
  • Rabies virus: Neurons
  • Influenza A virus: Erythroid precursors

Virus Life Cycle

  • Attachment, penetration, uncoating, gene expression and replication, assembly, maturation, and release are the stages
  • Processes vary based on the virus family.

Genome Replication and Viral Protein Production

  • Viral genomes replicate inside the host cell.
  • Types of genetic material vary among different viruses:
    • dsDNA viruses
    • ssDNA viruses
    • dsRNA viruses
    • (+)ssRNA viruses
    • (-)ssRNA viruses
    • ssRNA-RT viruses
    • dsDNA-RT viruses
  • Viral structural proteins like the capsid are synthesized.

Assembly of Virus

  • New virus particles are assembled
  • Hundreds to thousands of viral proteins assemble around viral nucleic acid to create a capsid
  • Host factors aid protein-protein interactions within the assembled virus particles that occur in the cytoplasm
  • Assembly occurs in the cytoplasm or nucleus.

Maturation

  • Virus maturation is where a virus becomes infectious.
  • The virion undergoes structural, chemical, and physical changes during maturation

Release of Virus

  • Newly formed viruses leave the host cell via lysis (commonly in non-enveloped viruses) or budding (commonly in enveloped viruses)
  • Host cell death is usually linked with lysis

Types of Life Cycle

  • Lytic cycle: Viruses replicate and kill host cell.
  • Lysogenic cycle: The viral genome integrates into the host genome; the virus does not immediately lyse the host cell; the virus becomes prevalent when host conditions are favorable

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Description

This quiz focuses on the intricate process of viral replication, including the essential steps that a virus undergoes to establish infection. Understanding these steps is crucial for developing antiviral strategies. Explore how viruses interact with host cells and the significance of each replication stage.

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