viral genomes and replications

What type of genomes can viruses have?

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

What does '+ ssRNA' mean in the context of viruses?

It has the same nucleotide sequence as viral mRNA.

What does '- ssRNA' mean in the context of viruses?

It has a base sequence complementary to viral mRNA.

What is meant by segmented linear RNA viruses?

These viruses have multiple segments of RNA that help them evolve and adapt rapidly.

What is reassortment in viral genetics?

The combination of segments from different viral strains during co-infection.

Why does the flu vaccine get updated annually?

Because of reassortment, which leads to adaptations in flu viruses that previous vaccines may not protect against.

How does the size of DNA viruses compare to RNA viruses?

DNA viruses are usually larger than RNA viruses.

What type of viruses infect bacteria and archaea?

Double stranded DNA viruses, commonly known as bacteriophages.

Why does the phylogenetic species concept not apply to viruses?

Viruses mutate and evolve too quickly to be classified using this concept.

How are virus genera typically named?

They are named with the suffix '-virus'.

What is the suffix used for viral families?

The suffix '-viridae'.

Name a basis for naming viruses.

Some viruses can be named based on their host.

What are the two main structural categories of viruses?

Naked viruses and enveloped viruses.

Name two shapes that viral capsids can have.

Helical or icosahedral.

What classification system categorizes viruses based on their genome composition?

Baltimore classification.

What types of transmission routes can viruses have?

Viruses can be transmitted via respiratory, sexual, or other means.

What does Class 1 and Class 7 in the Baltimore classification signify?

Both classes are double stranded DNA viruses.

What occurs in Class 2 of the Baltimore classification?

It involves single stranded DNA viruses that synthesize a minus strand.

What is unique about Class 3 viruses in the Baltimore classification?

They are double stranded RNA viruses that transcribe mainly from the minus strand.

What do Class 4 RNA viruses utilize for infection?

They are single stranded RNA viruses used directly as mRNA.

What does Class 5 indicate in the Baltimore classification?

They are negative-sense single stranded RNA viruses that transcribe a minus strand.

What is the defining feature of retroviruses?

They have a single stranded positive-sense RNA genome and use reverse transcription.

In a newly discovered virus that uses RNA-dependent RNA polymerase and has a negative-sense RNA genome, which Baltimore group does it belong to?

Class 5.

Which bacteriophage life cycle results in cell lysis?

Lytic cycle.

In the lytic cycle, how does the viral DNA enter the host cell?

Through penetration when the nucleic acid is injected.

What occurs during the biosynthesis phase of the viral life cycle?

The viral genome is replicated.

During the maturation phase, what happens to phage particles?

They assemble into mature bacteriophages.

What cycle allows viral DNA to be integrated into the host chromosome?

Lysogenic cycle.

What is induction in the lysogenic cycle?

The process where viral DNA is excised and the virus enters the lytic cycle.

How do animal viruses typically attach to host cells?

Through glycoprotein spikes binding to membrane receptors.

What happens to an animal virus' genome once it enters the cytosol?

It can complete all life cycle phases.

What is the difference in replication between DNA and RNA viruses?

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

What occurs during the maturation and assembly phase of a virus?

Mature virus particles are constructed and viral spikes are inserted into host cell membranes.

What is lysis in the context of viral infection?

The rupture of the host cell to release mature virus particles.

What characterizes an acute lysis virus infection?

It leads to a sudden increase of virions and is quickly overcome by the immune system.

What type of infection does an oncogenic virus cause?

It can transform normal cells into cancerous cells.

What defines a latent virus infection?

The virus remains in equilibrium with host cells and can reactivate later.

What is a persistent infection?

A slow increase of virion production over a long time span.

What are some factors that influence the nature of a viral life cycle?

Pathogenicity, transmission rate, and immune response.

Which virus is associated with causing cancer?

Oncoviruses.

What is significant about the Ebola virus?

It is a filovirus with high mortality and an acute presentation.

What makes the flu virus particularly dangerous?

It is transmitted easily via aerosols and can evolve rapidly due to genetic reassortment.

Why do segmented RNA genomes, like that of the influenza virus, evolve rapidly?

They can undergo recombination, leading to new strains during co-infections.

What virus is known for causing chickenpox and shingles?

Varicella zoster virus (VZV).

How is HIV classified and what does it cause?

HIV is a retrovirus that causes AIDS.

What distinguishes viroids from viruses?

Viroids lack a protein coating and consist solely of circular RNA.

How do prions propagate?

Prions convert normal proteins into misfolded forms, triggering a chain reaction of misfolding.

Which viral component is not found in all viruses?

Envelope.

What is the function of matrix proteins in viruses?

They may be required for the formation of new viral particles.

How do viruses typically replicate?

By taking control of the host cell and using its machinery.

What is the role of accessory proteins in viruses?

They may be required for infection and/or replication.

What is the role of hemagglutination assay?

To identify viruses based on their ability to agglutinate red blood cells.

How do viroids affect plant cells?

They can interrupt gene expression and interfere with normal plant growth.

What are 'inclusion bodies' related to?

They are compacted masses of damaged cell organelles resulting from viral infection.

What is a key feature of prions that distinguishes them from viruses?

Prions consist only of protein with no nucleic acid.

How are continuous cell lines obtained for virus cultivation?

From tumor cells or cancer cells that can divide indefinitely.

What is a plaque assay used for?

To determine the titer of infectious virions in a sample.

What is a common characteristic shared by all viruses?

They are obligate intracellular parasites.

What roles do viruses play in ecosystems?

They help limit host populations and recycle nutrients.

What is a virus's capsid primarily made of?

Protein subunits known as capsomers.

What determines the shape of a virus?

The structure of its capsid.

What allows enveloped viruses to be more flexible compared to naked viruses?

The presence of a surrounding envelope derived from the host cell.

What component of viruses can facilitate their entry into host cells?

Spikes of proteins embedded in the viral envelope.

What happens to the cellular membrane proteins during viral infection?

They are replaced by viral proteins during budding.

What happens to host cell proteins when infected by a virus?

Some of the host cell proteins may be replaced or modified by the viral proteins during infection.

How do viruses trigger immune responses in the host?

By presenting specific proteins in their capsid that can alert the immune system.