Bacteriophage and Animal Virus Replication

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Questions and Answers

What is the primary gas replaced in an anaerobic chamber after removing O2?

Helium

Nitrogen (correct)

Carbon Dioxide

Argon

What triggers the starvation response in microbes?

Presence of harmful chemicals

Accumulation of small signal molecules (correct)

Increase in temperature

Exposure to oxygen

What is the effect of moist heat compared to dry heat on microbial killing?

Moist heat is ineffective for killing microbes.

Moist heat is equally effective as dry heat.

Moist heat is less effective than dry heat.

Moist heat is more effective than dry heat. (correct)

Which of the following signals can diffuse quickly throughout a microbial cell to initiate responses?

Small signal molecules Signup and view all the answers

What kind of conditions can microbes potentially face in real-life environments?

Multiple stresses simultaneously Signup and view all the answers

What is required to kill endospores effectively?

High pressure and temperature Signup and view all the answers

Which agent is NOT commonly used to kill microbes?

Nitrogen Signup and view all the answers

How do many microorganisms react to molecular oxygen?

They are instantly killed Signup and view all the answers

What is the primary function of the viral capsid?

To package the viral genome and deliver it into the host cell Signup and view all the answers

What characteristic defines icosahedral viruses?

They have 20 identical triangular faces and exhibit rotational symmetry Signup and view all the answers

Which of the following describes how new viral pathogens emerge?

They emerge through mutations and interactions with unfamiliar animal hosts Signup and view all the answers

What role do glycoprotein spikes on the viral envelope serve?

They assist in attaching to and infecting host cells Signup and view all the answers

How do some viruses acquire their envelopes?

From the membrane of the host cell during the budding process Signup and view all the answers

What is a significant feature that may be found in certain icosahedral viruses?

They may have an envelope that comes from the host cell membrane Signup and view all the answers

What can result when a virus mutates?

It may gain the ability to infect new hosts Signup and view all the answers

Which of the following viruses are examples of those that persist in the wild?

Rabies virus and West Nile virus Signup and view all the answers

What characteristic distinguishes filamentous viruses?

Their capsid forms a long tube of protein. Signup and view all the answers

Which statement about viral genomes is true?

Viral genomes may contain polymerases not found in the host cell. Signup and view all the answers

What occurs during the lytic cycle of bacteriophages?

The host cell undergoes a lytic burst leading to cell death. Signup and view all the answers

In tailed viruses like T4 bacteriophages, what is the structural composition?

An icosahedral head supported by a helical neck. Signup and view all the answers

What triggers a bacteriophage to switch from the lysogenic cycle to the lytic cycle?

Environmental cues that threaten host cell survival. Signup and view all the answers

What aspect of phage injection into a bacterial cell is true?

The phage capsid remains outside attached to the cell surface. Signup and view all the answers

Which type of viral genome configuration is NOT possible?

Mixed RNA and DNA in a single genome. Signup and view all the answers

What is a requirement for all viruses regarding reproduction?

They require a host cell for genetic material replication. Signup and view all the answers

What is the first step in the lytic replication cycle of a bacteriophage?

Host recognition and attachment Signup and view all the answers

Which lifecycle does a bacteriophage typically follow when environmental cues threaten host cell survival?

Lytic cycle Signup and view all the answers

What remains outside the bacterial cell after a bacteriophage injects its genome?

The phage capsid or 'ghost' Signup and view all the answers

Which of the following sequences correctly represents the steps in the lytic replication cycle?

Host recognition, Genome entry, Assembly, Exit Signup and view all the answers

What typically dictates the decision between the lytic and lysogenic cycles for bacteriophages?

Environmental cues Signup and view all the answers

How do bacteriophages attach to their specific bacterial hosts?

By evolving to recognize specific receptor sites Signup and view all the answers

During the lytic cycle, what occurs immediately after a phage injects its genome into a bacterial cell?

The phage begins to reproduce progeny particles Signup and view all the answers

Which step follows 'Genome entry' in the lytic cycle of a bacteriophage?

Assembly of phages Signup and view all the answers

What role does RNA-dependent RNA-polymerase play in RNA viruses?

It transcribes their mRNA. Signup and view all the answers

Which of the following is true about the assembly of new virions in animal viruses?

Capsid and genome assembly may occur in the cytoplasm or nucleus. Signup and view all the answers

What mechanism do retroviruses use to integrate their genomic sequence into host DNA?

Reverse transcriptase Signup and view all the answers

How are progeny viruses released from a host cell?

Both lysis and budding methods. Signup and view all the answers

In the context of oncogenic viruses, what effect do they have on the host cell?

They transform the host cell to become cancerous. Signup and view all the answers

Which type of virus primarily utilizes the host's replication machinery?

DNA viruses Signup and view all the answers

Where do enveloped viruses typically acquire their membranes during the budding process?

From the host cell membrane or organelle membranes. Signup and view all the answers

What is a common characteristic shared by all animal viruses during protein synthesis?

Translation occurs in the cytoplasm. Signup and view all the answers

Study Notes

Bacteriophage Replication

Bacteriophages require a host cell for reproduction.
Infection requires:
- Host recognition and attachment
- Genome entry
- Assembly of virions
- Exit and transmission

Bacteriophages Infect a Bacterial Host

Most phages inject their genome into a cell through the cell envelope.
Phage capsid, often called a “ghost”, remains outside, attached to the cell surface.

Bacteriophage Life Cycles

All bacteriophages can undergo a lytic cycle.
Some bacteria can undergo a second lifecycle called the lysogenic cycle.
Environmental cues dictate which cycle occurs.
Events that threaten host cell survival trigger a lytic burst.

Animal Virus Replication Cycles

The form of the genome determines the life cycle of an animal virus.
DNA viruses utilize the host replication machinery.
RNA viruses use an RNA-dependent RNA-polymerase to transcribe their mRNA.
Retroviruses use a reverse transcriptase to copy their genomic sequence into DNA for insertion in the host chromosome.
All animal viruses make proteins with host ribosomes.
Translation occurs in the cytoplasm.
New virions are assembled:
- Capsid and genome
- May occur in the cytoplasm or nucleus
- Envelope proteins are inserted into a membrane, either cell or organelle membrane
Release of progeny viruses from the host cell occurs through:
- Lysis of the cell
- Budding:
  - Virus passes through the membrane
  - Membrane lipids surround the capsid to form the envelope
  - All enveloped viruses bud from a membrane, either the plasma membrane or an organelle membrane

Oncogenic Viruses

Many human cancers are caused by oncogenic viruses.
Oncogenic viruses transform the host cell to become cancerous.

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Description

Test your knowledge on the replication cycles of bacteriophages and animal viruses. This quiz covers the essential steps of infection, lifecycle variations, and the mechanisms viruses use to hijack host cells for reproduction. Refresh your understanding of virology and its complexities!