Viruses, Viroids, & Prions

A collection of flashcards covering key concepts from the lecture on viruses, viroids, and prions.

What is the definition of a virus?

A tiny particle made up of nucleic acid and protein that infects living organisms and causes disease.

What are viroids?

Short pieces of naked RNA that cause diseases, such as potato spindle tuber disease.

What are prions?

Proteinaceous infectious particles that can cause neurodegenerative diseases.

What is the function of the viral capsid?

To package the viral contents, protect the nucleic acid, and facilitate transport between cells.

How do viruses replicate?

Viruses must invade a host cell and hijack the host's metabolic machinery to replicate.

What distinguishes lytic and lysogenic cycles in bacteriophages?

Lytic cycle causes host cell death, while lysogenic cycle integrates into host DNA without killing the host.

What are the two types of viral infections in animals?

Latent infections and persistent infections.

What is the significance of the host range of a virus?

Host range defines the specific types of cells a virus can infect and replicate.

What are the characteristics of viruses that classify them?

1. Nucleic acids (DNA or RNA) 2. Virus particle structure 3. Size 4. Host they infect.

What nucleic acids can viruses contain?

Viruses can have either DNA or RNA, but never both.

What is a retrovirus?

A virus that has ssRNA and uses reverse transcriptase to produce DNA.

How do RNA viruses replicate in animal cells?

RNA viruses replicate their RNA in the cytoplasm using viral enzymes.

What role do oncogenes play in cancer?

Oncogenes transform normal cells into cancerous cells.

Define persistent viral infection.

A viral infection where the virus remains continuously active and is gradually released from cells.

What is the viral envelope?

A membrane layer that surrounds the viral capsid, obtained from the host cell's membrane.

What is the significance of the central dogma?

It describes the flow of genetic information from DNA to RNA to protein.

What types of cancer are associated with viruses?

Examples include liver cancer (Hepatitis B virus) and cervical cancer (Human papillomavirus).

What is the difference between single-stranded and double-stranded viral RNA?

Single-stranded RNA can be either sense (+) or antisense (−), while double-stranded RNA contains both strands.

How do viruses evade the immune response?

By using host cellular machinery and often inducing cell death to limit the spread of infection.

What is the significance of the viral genome?

The viral genome contains the genetic code necessary for producing viral proteins.

What specific infections do herpesviruses cause?

Cold sores and shingles are caused by herpesviruses.

What is the size range of viruses?

Viruses typically range from 20 to 1000 nm in size.

What is the role of spike proteins in enveloped viruses?

Spike proteins or glycoproteins help viruses attach and enter host cells.

What happens during the uncoating process in viral replication?

The capsid proteins of the virus are enzymatically removed, allowing access to the viral genome.

In which part of the host cell do DNA viruses replicate?

DNA viruses typically replicate in the nucleus of the host cell.

What is the lytic cycle of a bacteriophage?

A cycle where the phage causes lysis and death of the host cell through five main steps.

What is an example of a bacteriophage involved in the lytic cycle?

The T-even bacteriophage.

What does it mean for a virus to be an obligate intracellular parasite?

It means that the virus can only reproduce within a living host cell.

What are example viruses that can infect humans?

Influenza virus, Herpes virus, and Hepatitis C virus are examples.

How can viruses cross host species barriers?

Some viruses can infect different species through specific mutations or adaptations.

What is virus morphology based on?

Virus morphology is based on the configuration of the capsid structure.

How do enveloped viruses typically enter host cells?

Through receptor-mediated endocytosis or fusion with the host cell membrane.

What does the term 'ecological niche' refer to in microbiology?

The ecological niche refers to the specific environment or role a virus occupies in relation to its host.

What are capsomeres?

Subunits that make up the viral capsid.

How does the replication of RNA viruses differ from that of DNA viruses?

RNA viruses replicate in the cytoplasm, while DNA viruses use the nucleus for replication.

What disease does swine influenza cause?

Swine influenza is a viral infection that affects pigs but can also infect humans.

What is the function of reverse transcriptase in retroviruses?

It converts RNA into DNA, allowing integration into the host genome.

What is a prophage?

A bacteriophage genome that has integrated into a bacterial chromosome during the lysogenic cycle.

How do prions differ from viruses?

Prions are made solely of protein and do not have nucleic acids.

What infection is caused by the Varicella Zoster virus?

It can cause chickenpox and reactivation can lead to shingles.

What is a typical example of a viroid?

Potato spindle tuber viroid (PSTV) is a recognized example.

How can viral infections lead to cancer?

By integrating viral DNA into host DNA, leading to tumor development.

What type of cells do bacteriophages infect?

Bacteriophages specifically target bacterial cells.

What is the first step in viral replication?

Attachment of the virus to the host cell surface.

What is the purpose of the viral envelope?

To protect the viral genome and assist with entry into host cells.

What role do environmental factors play in the host range of a virus?

The presence of specific cellular factors and attachment sites dictate the host range.

How do persistent infections differ from acute infections?

Persistent infections are continuous and gradual, while acute infections typically present with sudden symptoms.

What happens to a cell during viral budding?

The virus acquires a portion of the host cell membrane by budding out, forming an envelope.

What characteristics make a virus an oncogenic virus?

The ability to integrate its genes into the host cell's DNA and induce changes leading to cancer.