Viruses, Viroids, & Prions

These flashcards cover the key concepts, definitions, and processes related to viruses, viroids, and prions as learned in the Microbiology 4000.01 course.

What is the basic definition of a virus?

A noncellular particle that contains a genome and can only replicate inside a host cell.

What type of virus infects bacteria?

Bacteriophage (phage).

What is a virion?

A complete virus particle.

What are acellular infectious biological agents?

Agents that have no plasma membrane, no binary fission, no ATP generation, and no protein synthesis capabilities.

What is an obligate intracellular parasite?

A virus that relies on a host cell for energy and replication machinery.

What structure surrounds the viral genome?

The nucleocapsid.

What are the two forms of nucleic acid that a virus can have?

DNA or RNA.

What is the function of a virus's capsid?

It is a protein coat that protects the viral genome and determines the shape of the virus.

What is the difference between naked and enveloped viruses?

Naked viruses consist of only a nucleocapsid, while enveloped viruses have a nucleocapsid enclosed in a lipid bilayer.

What is the role of viral attachment proteins?

They determine the host range and are recognized by the immune system.

What is a common shape of viral nucleocapsids?

Icosahedral.

What does the term 'lytic' mean in regards to phage infection?

A lytic phage infects the host cell, leading to the production and release of many new virions.

What is a lysogenic infection?

An infection where the viral genome integrates into the host genome and remains latent.

What is a prophage?

A viral genome that is integrated into a host cell's genome during a lysogenic infection.

What happens during viral reproduction?

Viruses recognize and attach to host cells, enter their genome, biosynthesize new virions, assemble them, and release them.

What is the burst size in viral replication?

The number of virions released after a lytic infection.

What are CRISPR systems in bacteria?

Bacterial systems that use sequences from phages to develop immunity against future infections.

What is antigenic drift?

Slow, small genetic changes in viruses that happen during replication.

What is antigenic shift?

A large, rapid genetic change that occurs through recombination and reassortment.

What is a viroid?

A virus-like infectious agent composed entirely of RNA, lacking a protective capsid.

What are prions?

Infectious agents made only of protein with no nucleic acid.

What is the primary function of Reverse Transcriptase in retroviruses?

To replicate the RNA genome into DNA.

How do RNA viruses typically replicate their genomes?

Using viral replicase enzymes in the cytoplasm of the host.

What is the Baltimore Classification?

A classification system for viruses based on their method of mRNA production.

What are spike proteins?

Glycoproteins on the surface of enveloped viruses that aid in attachment to host cells.

What distinguishes temperate phages from lytic phages?

Temperate phages can integrate their genome into the host genome and enter a lysogenic state.

What are filaments in the context of viruses?

Form of phage that does not directly kill the host, instead exiting through secretion.

Which type of viral genome is responsible for lysogenic conversion?

The prophage genes that provide new traits to the bacterial host.

What role do restriction enzymes play in bacterial defenses against phages?

They cut foreign DNA to protect against phage infections.

What is the role of methylation in bacterial immunity?

It helps distinguish self DNA from non-self (foreign) DNA.

What is the primary site for viral attachment and entry in animal cells?

Host cell receptors.

Which enzyme is responsible for synthesizing RNA from a DNA template?

RNA polymerase.

What happens during the biosynthesis phase of viral replication?

The viral genome and proteins are produced.

What occurs during the maturation stage of virus replication?

New virions are assembled prior to release.

How do viruses typically exit host cells?

By budding or exocytosis, which often spares the host cell.

What is a characteristic of naked viruses upon release?

They often cause host cell lysis.

What are the significant properties of prions?

They cause transmissible spongiform encephalopathies and are resistant to heat and proteases.

What is a common result of viral infection in terms of host pathology?

It can lead to cell death or changes in cell function and phenotype.

How does reverse transcription relate to the HIV lifecycle?

HIV RNA is converted into DNA, which integrates into the host genome.

What mutation mechanism leads to increased viral diversity?

Antigenic drift due to replication errors.

What is the function of viral proteases?

They cleave large viral polyproteins into functional proteins.

What are the major steps in viral replication?

Recognition and attachment, genome entry, biosynthesis, assembly, and release.