Question

Which of the following leads to the destruction of the host cells? a. lysogenic cycle b. lytic cycle c. prophage d. temperate phage

Short answer

b. lytic cycle

Step-by-step solution

Understand the Terminology

First, recognize the key terms: lysogenic cycle, lytic cycle, prophage, and temperate phage. Each term relates to viral replication processes.

Review the Lytic Cycle

In the lytic cycle, the virus hijacks the host cell’s machinery to replicate its own genetic material, producing new viruses. The host cell eventually bursts (lyses), releasing the new viruses and destroying the host cell.

Review the Lysogenic Cycle

In the lysogenic cycle, the viral DNA integrates into the host cell’s genome and replicates along with it without causing immediate harm. The host cell remains alive and functions normally.

Evaluate Prophage and Temperate Phage

A prophage is viral DNA embedded in the host cell’s DNA during the lysogenic cycle. A temperate phage is a virus capable of both lysogenic and lytic cycles.

Identify the Correct Answer

Considering the processes, the lytic cycle leads to the destruction of the host cell as it results in cell lysis to release new viruses.

Key concepts

lytic cycle

The lytic cycle is a process in which a virus takes control of a host cell’s machinery to replicate its own genetic material. This cycle can be divided into several key stages:

• Attachment: The virus attaches itself to the surface of the host cell.
• Penetration: The viral genetic material (DNA or RNA) is injected into the host cell.
• Replication and Synthesis: The host cell's machinery is used to replicate the viral genome and synthesize viral proteins.
• Assembly: New virus particles are assembled from the replicated genetic material and proteins.
• Release: The host cell bursts (lyses), releasing the new viruses into the environment.

This cycle leads to the destruction of the host cell, as it is lysed to release the new viruses, allowing them to infect neighboring cells.

lysogenic cycle

In contrast to the lytic cycle, the lysogenic cycle involves the viral DNA integrating into the host cell's genome. Here’s how it works:

• Attachment and Penetration: The virus attaches to the host cell and injects its DNA.
• Integration: The viral DNA is incorporated into the host cell’s chromosome and becomes a prophage.
• Replication: The host cell replicates normally, copying the viral DNA along with its own.

During the lysogenic cycle, the virus does not immediately harm the host cell. The viral DNA can remain dormant for an extended period. However, environmental triggers or stress can cause the prophage to exit the host genome and enter the lytic cycle, leading to the destruction of the host cell.

prophage

A prophage is a form of viral DNA that is integrated into the DNA of a host cell during the lysogenic cycle. Here is how it functions:

• Integration: The viral genome integrates into the host’s DNA.
• Replication: Each time the host cell divides, it replicates the prophage along with its own DNA.
• Induction: Under certain conditions (like stress or UV light), the prophage can be excised from the host genome and enter the lytic cycle, starting to produce new viral particles.

As long as it remains dormant, the prophage does not harm the host cell. It ensures the virus's survival and spread through the host's cell divisions without destroying the host cells immediately.

temperate phage

A temperate phage is a type of virus that can choose between two replication pathways - the lytic and lysogenic cycles. Here’s what makes it unique:

• Lytic Cycle: In this pathway, the temperate phage follows the lytic process, leading to the destruction of the host cell to produce and release new viral particles.
• Lysogenic Cycle: Alternatively, it may integrate its DNA into the host cell’s genome as a prophage, remaining dormant and replicating along with the host cell's DNA without causing immediate harm.

The ability to switch between these cycles allows temperate phages to respond to environmental conditions, ultimately improving their survival and propagation capabilities. This dual pathway offers flexibility: they can rapidly reproduce if conditions are favorable (lytic cycle) or lie in wait within the host cell if conditions are adverse (lysogenic cycle).