Viral Infections and Replication Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What occurs during a productive infection?

Infecting virus is always defective.

The viral genome is absent in host cells.

All viral genes are expressed and infectious virus is produced. (correct)

The host immune response is fully activated.

What is the main characteristic of an abortive infection?

Establishing latent infection in host cells.

Expression of all viral genes.

Production of infectious progeny fails. (correct)

Complete viral replication and production.

What differentiates latent infection from chronic infection?

Chronic infections have minimal or absent viral gene replication.

Latent infections do not involve viral genome replication or virion production. (correct)

Latent infections lead to immediate immune response activation.

Latent infection produces more virions than chronic infection.

What is the purpose of latent genes during latency?

To prevent host immune response and maintain the virus in the host. Signup and view all the answers

What happens at the end of the latent period for a virus?

Marked disorder of cell function and changes in morphology occur. Signup and view all the answers

Which factor is NOT associated with latent infection?

Continuous replication of the viral genome. Signup and view all the answers

Why might a virus undergo an abortive infection?

The host cell is in a nonpermissive state. Signup and view all the answers

What is one consequence of latent infection for the host?

Intracellular viral persistence without producing infectious virus. Signup and view all the answers

What is the primary characteristic of cytopathic effect (CPE)?

Lysis and death of cells Signup and view all the answers

Which viral replication step involves the removal of capsid proteins?

Uncoating Signup and view all the answers

Which of the following is NOT typically observed as a change in CPE?

Enhanced cell division Signup and view all the answers

What role does pH play in the viral life cycle during penetration?

Favors uncoating Signup and view all the answers

What is the result of viral genome replication during the viral growth cycle?

Assembly of complete virus particles Signup and view all the answers

Which step follows immediately after the uncoating of the viral genome?

Gene expression Signup and view all the answers

What type of cells do viruses typically target to induce CPE?

Eukaryotic cells Signup and view all the answers

Which of the following events is classified as a late event in viral replication?

Release Signup and view all the answers

What is the term used to describe the types of cells and tissues in which a virus can replicate?

Tropism Signup and view all the answers

Which type of virus typically uses the host cell's RNA polymerase for mRNA synthesis?

Most DNA viruses Signup and view all the answers

Which of the following viruses can infect only human cells?

Poliovirus Signup and view all the answers

What types of proteins are synthesized as early proteins during viral replication?

Enzymes required for replication Signup and view all the answers

Which of the following statements about the viral genome is correct?

All DNA viruses consist of double-stranded DNA except for parvoviruses. Signup and view all the answers

During which phase do the components of the virus assemble into complete virions?

Maturation Signup and view all the answers

What generally happens during the release of new virions from host cells?

It may or may not kill host cells. Signup and view all the answers

What specific receptor does the rabies virus attach to for entry into the host cell?

Acetylcholine receptor Signup and view all the answers

What is the term used for viruses that infect bacteria?

Bacteriophages Signup and view all the answers

What characterizes the eclipse period during viral replication?

Loss of measurable infectivity Signup and view all the answers

How long does it typically take for a single virion to replicate within a host cell?

Approximately 10 hours Signup and view all the answers

What follows the eclipse period in the viral replication cycle?

Rise period Signup and view all the answers

Which of the following statements is true regarding the yield of infectious virus per cell?

It varies widely, from modest numbers to over 100,000 particles Signup and view all the answers

What is a defining feature of viral multiplication compared to other forms of reproduction?

It can produce hundreds of virus particles from a single initial particle Signup and view all the answers

What is the duration of the virus replication cycle for picornaviruses?

About 6 to 8 hours Signup and view all the answers

What happens to the infecting virion soon after it enters a host cell?

It is disrupted and loses measurable infectivity Signup and view all the answers

Study Notes

Viral Replication

Viruses multiply only inside living host cells (bacteria or animal cells)
Host cells provide energy and machinery for viral protein and nucleic acid synthesis
Viruses that infect bacteria are called bacteriophages
Viral replication can be described using a growth curve or a stepwise description of cellular events

Viral Growth Curve

Shows the amount of virus produced over time after infection
The eclipse period is where no infectious virus is detectable in the infected cells.
The rise period follows where there is rapid increase in viral progeny (increase in virus particles in the cell).
The eclipse period is a phase of intense synthetic activity within the cell, to support viral needs
The duration varies depending on the virus and host cell type.
This time varies from minutes to hours

Viral Replication Cycle

Attachment and Penetration: The virus attaches to the cell membrane and enters the host cell
Uncoating: Viral genome is released from the capsid (protective protein coat).
Early Events: Early mRNA and proteins are synthesized which are used to replicate the viral genome.
Middle Events: Viral genome replication occurs
Late Events: Late mRNA and proteins are then synthesized which are structural capsid proteins
Assembly: Progeny virions are assembled
Release: Progeny virions are released from the host cell

Types of Viral Infections

Productive Infections: Viral genomes replicate inside host cell leading to virus production
Abortive Infections: Cell is non-permissive or the infecting virus is defective; no complete progeny virus are made
Latent Infections: Minimal viral gene expression occurs; viral genome is present, but no infectious progeny viruses are formed.

Cytopathic Effect (CPE)

Cell morphology alterations and function disorder
Follows the end of latent period
Lysis and death of cells
Important diagnostic tool, however, not all viruses cause CPE

Diagnostic Application of CPE

Virus growth in cell culture shows CPE, providing a presumptive diagnosis.
Change in appearance of infected cells (size, shape, fusion to form multinucleated giant cells)
Indication that the virus infected cells are dying or dead.
Time taken for CPE, and cell type is important in diagnostic identification

Viral Replication in Eukaryotic Cells

Parental virus particle attaches to cell membrane and penetrates
Viral genome is uncoated releasing the viral genome
Early mRNA and encoded proteins are synthesized for viral genome replication
Late mRNA and proteins are synthesized: these are structural capsid proteins
Progeny virions are assembled and released from host cell

Viral Genomes

Most DNA viruses replicate in the cell nucleus using host cell RNA polymerase to synthesize mRNA. Double-stranded DNA is the genome except for some with single-stranded DNA.
Most RNA viruses replicate in the cytoplasm, except for HIV and Influenza virus. Their genomes are typically single-stranded RNA, with some exception for a double stranded RNA genome.

Attachment, Penetration & Uncoating

Different means exist for how different viruses enter their host cells, either via endocytosis (engulfing), or fusion of their envelope with host cell membrane
The process of uncoating begins within the vesicle formed in endocytosis, influenced by low pH which aids in freeing the nucleic acid
Rupture or fusion deposits the viral genomic material into the cytoplasm; this forms the infectious nucleic acid for the virus

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on the characteristics of productive, abortive, latent, and chronic viral infections. Explore the viral replication cycle, including the role of capsid proteins and cytopathic effects. This quiz covers key concepts necessary for understanding the complexities of viral behavior and their impact on hosts.