Lytic and Lysogenic Cycles Quiz

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Questions and Answers

What happens during the lysogenic cycle of a virus?

Viral proteins are produced and the host cell is destroyed.

Viral DNA is replicated along with the host's DNA without harming the host cell. (correct)

New virus particles are assembled and released into the environment.

The virus fully takes over the host cellular machinery immediately.

Which of the following statements correctly distinguishes the lytic cycle from the lysogenic cycle?

No viral protein synthesis occurs during the lytic cycle.

The lytic cycle does not produce virions.

Lysogenic cycles always lead to host cell death.

The lytic cycle results in the destruction of the host cell. (correct)

What is a prophage?

A new virus particle produced during the lytic cycle.

The mechanism by which the virus hijacks the host cell.

A form of viral protein synthesized in the host cell.

The viral genome integrated into the host genome during the lysogenic cycle. (correct)

During which viral replication mode does viral genome replication occur independently of the host cell's replication mechanism?

Lytic cycle Signup and view all the answers

Which statement best describes the infectivity rate of viruses during the lytic cycle?

It is high because multiple virions can be produced and released. Signup and view all the answers

What is the key difference between the lytic and lysogenic cycles concerning the host cell?

The lytic cycle leads to the death of the host cell. Signup and view all the answers

In which stage of the bacteriophage life cycle does the virus integrate its genome into the bacterial chromosome?

Lysogenic phase Signup and view all the answers

Which component of a bacteriophage is responsible for recognizing the bacterial cell for attachment?

Capsid proteins Signup and view all the answers

What does the term 'prophage' refer to in the lysogenic cycle?

The integrated phage genome within a host's genome. Signup and view all the answers

What is a common outcome of the lytic cycle for the host bacterium?

The host bacterium undergoes cell lysis and dies. Signup and view all the answers

How does a lysogenic bacteriophage replicate its genome?

Passively during bacterial cell division. Signup and view all the answers

Which type of nucleic acid can a bacteriophage possess in its genome?

Double-stranded DNA or RNA, single-stranded DNA or RNA Signup and view all the answers

Which of the following best describes a bacteriophage?

A non-living acellular particle that cannot reproduce outside a host. Signup and view all the answers

What is a primary reason the lysogenic cycle is considered a non-virulent infection?

It integrates the viral genome without harming the host. Signup and view all the answers

The lytic cycle of a bacteriophage can result in which of the following outcomes?

The bursting of the host cell to release new virions. Signup and view all the answers

Study Notes

Lysogenic Cycle

Viral DNA replicates using the host cell's machinery.
Replication occurs during host cell division without harming the host.
Host cell's DNA replication machinery cannot distinguish between viral and host DNA.

Lytic Cycle

Viral DNA and proteins are replicated and translated using host cellular processes.
Viral proteins assemble into new virions (virus particles).
Host cell bursts, releasing millions of virions, causing high infectivity rates.

Lytic vs. Lysogenic Cycles

Lytic: Virus hijacks host systems, produces virions, and kills the host cell.
Lysogenic: Virus does not fully control the host; viral genome replicates with host genome without killing the host.
Lysogenic cycle: Viral genome (prophage) integrates into the host genome.
Lytic cycle: Genome replication is independent of the host's replication mechanism.
Lysogenic cycle yields fewer viral genomes than the lytic cycle.
Lytic cycle ends with numerous new virions; lysogenic cycle ends with a prophage.
Lytic cycle is faster; lysogenic cycle is slower and establishes symbiosis.
Lysogenic cycle can transition to the lytic cycle, but not vice versa.

Bacteriophages

Viruses that infect bacteria.
Discovered in 1915 (Twort) and confirmed in 1917 (d'Hérelle).
Obligate intracellular parasites; cannot reproduce outside a host.
Replicate via lytic, lysogenic, or both cycles.

Bacteriophage Structure

Capsid (protein coat) enclosing the nucleic acid genome.
Sheath connecting the capsid to the tail.
Tail fibers for attachment to the host cell.

Lysogenic Life Cycle (Bacteriophage)

Temperate or non-virulent infection; does not immediately kill the host.
Example: Lambda phage.
Phage genome integrates into the bacterial chromosome (prophage).
Prophage replicates passively with the host genome.
Host bacterium remains relatively unharmed.

Lytic Cycle (Bacteriophage)

Virulent infection; kills the host.
Example: T phage.
Steps: Adsorption (attachment), penetration, replication & biosynthesis, maturation, lysis & release.
Phage proteins lyse the host cell to release new virions.

Transition from Lysogenic to Lytic Cycle

Lysogenic state is not permanent.
Environmental factors (UV light, chemicals, nutrient deficiencies) can trigger induction.
Prophage excises from the bacterial chromosome, circularizes, and enters the lytic cycle.

Lysogenic Conversion

Phenotypic changes in bacteria harboring prophages.
Prophage genes (e.g., toxin or resistance genes) can alter host traits.
Examples: Increased virulence in Vibrio cholerae and Clostridium botulinum.

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Description

Test your knowledge on the lytic and lysogenic cycles of viruses. This quiz covers the mechanisms of viral replication, host cell interactions, and the key differences between both cycles. Explore how viruses affect their hosts in various stages of infection.