Virus and Bacteriophage Replication

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Questions and Answers

What happens to a prophage during host cell division?

It remains in the cytoplasm.

It is copied along with host DNA. (correct)

It is destroyed along with host DNA.

It initiates a lytic cycle.

Which of the following factors can trigger the proliferation of new phages from a prophage?

Host cell apoptosis

High nutrient availability

UV radiation or certain chemicals (correct)

Bacterial replication

How do prophages potentially benefit their host bacterium?

By providing new functions to the bacterial genome. (correct)

By enhancing bacterial cell division.

By preventing viral infection.

By decreasing metabolic activity.

What is true about permissive cells in relation to viral infection?

They allow the production of progeny virus particles. Signup and view all the answers

In what location do most DNA viruses assemble during replication?

In the nucleus Signup and view all the answers

Which type of virus can establish both productive and nonproductive relationships with host cells?

Temperate viruses Signup and view all the answers

Which bacterium produces diphtheria toxin when infected by a specific phage?

Corynebacterium diphtheriae Signup and view all the answers

What defines a lytic or virulent virus?

It can only establish a productive relationship. Signup and view all the answers

What is the primary purpose of viral replication from the virus's perspective?

To reproduce and survive Signup and view all the answers

What type of genetic material do most known bacteriophages possess?

Double-stranded DNA Signup and view all the answers

Which cycle culminates in the host cell bursting and releasing virions?

Lytic cycle Signup and view all the answers

What is formed when a phage's DNA integrates with the bacterial chromosome?

Prophage Signup and view all the answers

Which of the following describes a temperate phage's behavior?

It can switch between lytic and lysogenic cycles Signup and view all the answers

What happens during the lytic cycle of bacteriophage replication?

New phages are produced and the host cell dies Signup and view all the answers

In what way are bacteriophages useful in the medical and pharmaceutical industry?

They can act as antibacterial agents in phage therapy Signup and view all the answers

Which of the following best describes a virulent bacteriophage?

It reproduces within the host and causes cell lysis Signup and view all the answers

What is the first step in the animal virus replication cycle?

Adsorption to the host cell Signup and view all the answers

Which of the following stages involves the production of viral nucleic acids and proteins?

Replication of virus nucleic acids and protein synthesis Signup and view all the answers

Which term describes a virus entering a state where no new virus is produced but viral genetic material persists?

Non-productive response Signup and view all the answers

What does the term 'adsorption' specifically refer to in the virus replication cycle?

The random collision of a virion with a host cell Signup and view all the answers

What kind of receptor proteins do viruses attach to during the adsorption stage?

Surface proteins necessary for cell functions Signup and view all the answers

Which of the following best describes the lytic cycle in animal viruses?

May or may not result in lysis of the host cell Signup and view all the answers

Which component of a virion is often involved in attaching to host cell receptors?

Capsid structural proteins Signup and view all the answers

What is a key feature of the proteins that allow viruses to attach to host cells?

They are highly specific to certain host cell receptors Signup and view all the answers

What is the initial step of herpes virus replication?

Fusion with host cell membrane Signup and view all the answers

During which phase are the major structural proteins of the herpes virus synthesized?

Late transcription phase Signup and view all the answers

What is the role of the viral protease in herpes virus replication?

To cleave long protein strands for capsid maturation Signup and view all the answers

Which step follows viral DNA replication in the herpes virus life cycle?

Packaging of DNA into capsids Signup and view all the answers

In the poxvirus replication cycle, which process occurs first?

Attachment of the virus Signup and view all the answers

How does parvovirus B19 enter the host cells?

Through coated pits mediated internalization Signup and view all the answers

What type of genetic material is delivered into the nucleus during the replication of parvovirus B19?

Single-stranded DNA Signup and view all the answers

Which process does NOT occur in the maturation of herpes viruses?

Synthesis of viral mRNA Signup and view all the answers

What is the first step in the lysogenic cycle of a virus?

Viral genome enters cell Signup and view all the answers

What happens during the initial budding process of virus release?

Daughter viruses can lead to loss of cell membrane permeability Signup and view all the answers

What triggers the viral genome to detach from the host cell's DNA in the lysogenic cycle?

High stress levels and hormones Signup and view all the answers

Which protein attracts the completed nucleocapsid during the virus release process?

Matrix or M protein Signup and view all the answers

How does a virus like herpes enter the lysogenic cycle?

After first entering the lytic cycle then moving to lysogenic Signup and view all the answers

What role does the endoplasmic reticulum play in the release of poxviruses?

It programs the formation of envelope membranes. Signup and view all the answers

What is a common characteristic of retroviruses, except HIV, regarding cell death?

They reproduce without causing cell death. Signup and view all the answers

What is a characteristic feature of the lytic cycle?

It leads to the death of the host cell. Signup and view all the answers

Study Notes

Virus Replication

Viruses must enter a host cell to replicate, allowing for the virus to reproduce and survive
Most bacteriophages have double-stranded DNA.
Viruses generate copies of their genome and package them into new virions, allowing infection of new hosts.

Bacteriophage Replication

The replication cycle of bacteriophages is well-understood and researched,
Bacteriophages are viruses that infect bacteria and are used in medical and pharmaceutical applications.
Some bacteriophages can be used to create cloning and expression vectors.
Bacteriophages are also used for industrial production:
- They can be used to express heterologous proteins, which are essential for the creation of pharmaceuticals, vaccines, and antibodies.

Lytic Cycle

In the lytic cycle, a phage hijacks a host cell, using it to create new phage particles.
The host cell is then lysed, bursting and releasing new virions.

Lysogenic Cycle

The phage DNA integrates with the host chromosome to form a prophage, which replicates along with the host's own DNA.
Prophages can remain dormant and be transmitted to daughter cells during cell division.
Lysogenic cycles are activated via triggers such as UV radiation or presence of specific chemicals, resulting in new phage production.
Prophages can sometimes benefit the host bacterium by providing new functions to the bacterial genome.

Animal Virus Replication

Animal viruses are often species- and cell-specific.
There are six basic stages in the replication cycle of animal viruses.
Virus replication depends on the interaction between the virus and the host cell.
- Permissive cells allow for viral replication, while nonpermissive cells do not but may allow for viral transformation, a change in the host cell's phenotype.

Stages of Animal Virus Replication

Adsorption or attachment: the virus binds to the host cell's surface via a random collision. Virion attachment proteins bind to specific receptors on the host cell membrane.
Penetration or entry: the virus enters the cell using different mechanisms like fusion, endocytosis, or direct penetration.
Un-coating: the virus releases its nucleic acid into the cell's cytoplasm.
Replication of virus nucleic acids and protein synthesis: the virus uses the cell's machinery to produce more nucleic acids and proteins.
Assembly of virion components: the virus uses the synthesized proteins to assemble new virion components.
Maturation: the newly assembled virions mature and acquire functional components.
Release of mature viruses: the new virions are released from the cell, usually by budding or lysis.

Animal Virus Lysogenic Cycle

The lysogenic cycle occurs when the viral genome integrates into the host cell's genome.
The viral genome is replicated along with the host cell's DNA.
The viral genome may remain integrated indefinitely, or it can be triggered to enter the lytic cycle.

Herpes Virus Replication

These viruses have large DNA genomes and infect non-dividing cells.
Their replication cycle is complex and includes early and late transcription phases.
The late transcription phase produces mRNAs encoding structural proteins, such as capsid proteins, tegument proteins, and envelope glycoproteins.
They assemble in the nucleus, where they acquire their envelope.
They are released by exocytosis.

Poxvirus Replication

Poxviruses replicate in the cytoplasm of the host cell.
Their replication cycle is complex and involves synthesis of early, intermediate, and late mRNAs.
They are released by budding or lysis.

Parvovirus B19 Replication

Parvoviruses are small, single-stranded DNA viruses.
They bind to P antigen (globoside) on the host cell surface and enter the cell via endocytosis.
They release their DNA into the nucleus, where it replicates.
They are released by lysis when the host cell dies.

Budding

Budding is a process where a virus acquires its envelope from the host cell membrane.
The envelope is coated with specific viral proteins and the nucleocapsid binds to the membrane, enabling the virus to bud out of the cell.

Release

Some viruses are released through exocytosis.
Others are released through lysis, which destroys the host cell.
The release of too many virions can lead to cell death.
Retroviruses, except HIV, replicate without cell death.

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Description

Explore the intricate processes of virus and bacteriophage replication. This quiz delves into the lytic and lysogenic cycles, as well as the significance of bacteriophages in biotechnology and medicine. Test your understanding of how viruses reproduce within host cells and their practical applications.