lytic cycle pt 1

What is a bacteriophage?

A virus that infects bacteria.

What is a virulent phage?

A bacteriophage that only undergoes the lytic cycle, reproducing inside the host and eventually destroying the bacterial cell.

What is a temperate phage?

A bacteriophage that can undergo either the lytic cycle or the lysogenic cycle.

What is the difference between a virulent phage and a temperate phage?

Virulent phages only undergo the lytic cycle, while temperate phages can undergo either the lytic or lysogenic cycle.

What are the steps of the lytic cycle?

1. Attachment (adsorption),

2. Penetration (injection of viral DNA),

3. Biosynthesis (viral DNA and proteins are made),

4. Self-assembly (new viruses are assembled),

5. Release (host cell lyses and releases new viruses)

What happens during attachment in the lytic cycle?

The bacteriophage attaches to receptors on the bacterial cell.

What happens during penetration in the lytic cycle?

The bacteriophage injects its DNA into the bacterial cell.

What happens during biosynthesis in the lytic cycle?

The host cell synthesizes viral DNA and viral proteins using the instructions from the viral DNA.

What happens during self-assembly in the lytic cycle?

Viral components assemble into new bacteriophages, and viral DNA is packaged into the capsids.

What happens during release in the lytic cycle?

The bacterial cell lyses (bursts), releasing newly assembled bacteriophages.

What is the lysogenic cycle?

A cycle in which viral DNA becomes incorporated into the bacterial chromosome and remains dormant while the host cell grows and divides.

What is a prophage?

Viral DNA that has integrated into the bacterial chromosome during the lysogenic cycle.

What happens to viral DNA when a bacterial cell grows and divides during the lysogenic cycle?

The prophage is copied along with the bacterial chromosome and passed to each daughter cell.

Does the bacterial cell normally die during the lysogenic cycle?

No. The bacterial cell remains alive and continues growing and dividing while carrying the prophage.

What causes a temperate phage to enter the lysogenic cycle instead of the lytic cycle?

Environmental conditions and signals can influence the decision. When conditions are unfavorable for rapid viral reproduction, such as limited host availability, lysogeny allows the viral DNA to remain in the host and replicate with it.

What is induction?

The process in which a prophage leaves the bacterial chromosome and enters the lytic cycle.

What can cause induction?

Stress or DNA damage to the bacterial cell, such as exposure to UV radiation or certain chemicals.

What happens after induction?

Viral DNA separates from the bacterial chromosome, viral components are produced, new bacteriophages assemble, and the host cell eventually lyses.

What is an advantage of the lytic cycle for a virulent phage?

It rapidly produces many new viruses without waiting for the host cell to divide.

What is a disadvantage of the lytic cycle?

The host cell is destroyed, so the virus must find another suitable host to reproduce.

What is an advantage of the lysogenic cycle for a temperate phage?

Viral DNA can remain inside a living host and be copied every time the host cell divides, allowing the virus to persist without immediately destroying the host.

What is a disadvantage of the lysogenic cycle?

The virus does not immediately produce large numbers of new phages. It depends on the host cell surviving and reproducing.

Why might a temperate phage choose lysogeny when healthy host cells are scarce?

It can preserve its viral DNA inside a host instead of immediately destroying the host, allowing the viral DNA to be copied as the host reproduces.

Why might a phage enter the lytic cycle when a host cell is unhealthy or damaged?

The host may not survive much longer, so producing and releasing new viruses before the host dies can improve the chance of viral survival.