Quiz: Microbiology viral replication cycles

What is viral replication?

Viral replication is the process by which viruses produce new viral particles within a host cell.

List the main stages of viral replication.

- Attachment - Penetration - Uncoating - Replication - Assembly - Release

True or False: Viruses can replicate independently.

False. Viruses require a host cell for replication as they lack the machinery to do so on their own.

Fill in the blank: The stage where viral genetic material is released is called _______.

Uncoating

How do viruses attach to host cells?

Viruses use specific proteins on their surface that bind to receptors on the host cell's membrane.

Define the term 'host range'.

Host range refers to the spectrum of host cells a virus can infect, influenced by receptor compatibility.

What happens during the replication stage?

Viral genetic material is replicated using the host's cellular machinery to produce viral RNA or DNA.

Cause → Effect: What leads to viral release?

After assembly, new viruses exit the host cell, often causing cell lysis or budding.

Compare assembly and replication in viral cycles.

Assembly involves packaging of replicated viral components, while replication is the copying of the viral genome.

True or False: All viruses have DNA as their genetic material.

False. Some viruses have RNA, while others have DNA as their genetic material.

What is the significance of viral attachment?

Attachment is crucial for infection as it determines whether a virus can enter a specific host cell.

What does the term 'lysis' refer to?

Lysis is the breaking down of the host cell membrane, resulting in the release of new viral particles.

List two types of viral replication methods.

- Lytic Cycle - Lysogenic Cycle

What role does the host cell play in viral replication?

The host cell provides the necessary machinery, energy, and environment for viral replication and assembly.

True or False: Viruses can be treated with antibiotics.

False. Antibiotics target bacterial infections, not viral infections.

Describe the ‘release’ stage briefly.

Release is when newly formed viruses exit the host cell, either by cell lysis or budding off.

What is the primary characteristic of the lytic cycle?

The lytic cycle results in the immediate destruction of the host cell, releasing new viral particles.

True or False: The lysogenic cycle causes cell death immediately.

False. The lysogenic cycle integrates viral DNA into the host genome, allowing replication without immediate cell death.

Lytic cycle → characteristics:

- Rapid replication - Host cell lysis - Release of virions

Fill in the blank: In the lysogenic cycle, viral DNA is incorporated into the _____ of the host cell.

genome

What happens during the lysogenic cycle?

The virus integrates its genetic material into the host's DNA, remaining dormant until triggered to enter the lytic cycle.

Difference between lytic and lysogenic cycles?

The lytic cycle destroys the host cell immediately, while the lysogenic cycle allows the host to live and replicate.

Cause → Effect: Lytic cycle activation leads to...

destruction of the host cell and viral replication.

What triggers the switch from the lysogenic to lytic cycle?

Environmental stressors, such as UV light or certain chemicals, can activate the lytic cycle.

Lysogenic cycle → benefits to the virus:

- Evasion of immune response - Prolonged survival in host - Opportunity for genetic variation

True or False: All viruses undergo both lytic and lysogenic cycles.

False. Not all viruses have a lysogenic cycle; some only replicate via the lytic cycle.

What is a prophage?

A prophage is the viral DNA integrated into the host genome during the lysogenic cycle.

Comparison: Lytic vs. Lysogenic cycles in terms of duration.

Lytic cycle is short (hours), while lysogenic cycle can last for years.

Give an example of viruses that can undergo lysogenic cycles.

Bacteriophages, like λ phage, and some herpesviruses.

Fill in the blank: The lytic cycle often results in the release of _____ new viruses.

hundreds to thousands

What is the main method of host cell destruction in the lytic cycle?

Host cell lysis, caused by the accumulation of viral particles and enzymatic breakdown of the cell membrane.

Consequences of the lysogenic cycle on the host organism?

May lead to latent infections, increased viral spread during cell division.

Define viral entry.

The process by which viruses gain access to host cells, initiating infection.

True or False: All viruses enter cells the same way.

False. Different viruses utilize various entry mechanisms such as fusion and endocytosis.

What is receptor-mediated endocytosis?

A process where viruses bind to specific cell receptors, triggering internalization via vesicles.

List two viral entry mechanisms.

- Direct fusion - Endocytosis

How does viral fusion work?

Virus envelope merges with host cell membrane, releasing viral contents into the cell.

Fill in the blank: Viruses that use _______ often require specific receptors on the host cell.

receptor-mediated endocytosis

Comparing endocytosis and fusion: What’s the main difference?

Endocytosis involves vesicle formation; fusion directly merges viral and host membranes.

What happens during clathrin-mediated endocytosis?

Viruses bind to receptors, triggering clathrin coat formation, leading to vesicle internalization.

How do non-enveloped viruses typically enter cells?

They often use endocytosis or direct penetration without needing a lipid membrane.

True or False: All viruses require energy to enter host cells.

False. Some entry mechanisms do not require energy, such as passive diffusion.

Describe how enveloped viruses utilize membrane fusion.

Enveloped viruses have lipid bilayers that merge with host cell membranes, facilitating entry.

Cause → Effect: What causes viral entry via endocytosis?

Viral binding to host receptors causes cellular uptake through vesicle formation.