Micro F Comprehensive Biology of Viruses, Viroids, and Prions

Vocabulary practice flashcards covering viral biology, bacteriophage replication, animal virus pathogenesis, viroids, and prions.

Virus

An acellular infectious agent possessing either a DNA or RNA genome, lacking cellular membranes, cytosol, organelles, and metabolic machinery.

Virion

The extracellular state of a virus, consisting of a nucleic acid core enclosed by a protein capsid, and sometimes an outer phospholipid envelope.

Capsid

The outer protein coat that encloses and protects the viral nucleic acid genome.

Capsomeres

The small, repeating protein subunits that assemble to compose a viral capsid.

Viral Envelope

An outer phospholipid bilayer and protein layer acquired from the host cell membrane that surrounds the capsid in some viruses.

Spikes

Virally encoded glycoproteins that protrude from the surface of an enveloped virus and mediate host cell recognition and binding.

Naked Virus

A virus or virion that lacks a surrounding phospholipid envelope around its protein capsid (also called nonenveloped).

Generalist (Virus)

A virus capable of infecting multiple host species or many distinct cell types within a host (such as the COVID-19 virus binding ACE2 receptors).

Bacteriophage

A virus that specifically infects and replicates within bacterial cells.

Lytic Cycle

A viral replication cycle consisting of five stages (attachment, entry, synthesis, assembly, and release) that rapidly culminates in host cell lysis and death.

Lysozyme

A viral enzyme that degrades bacterial peptidoglycan to allow phage entry into the host cell and facilitate release during lysis.

Lysogeny

A modified bacteriophage replication cycle in which the viral genome integrates into the bacterial chromosome instead of immediately degrading it.

Temperate Phage

A bacteriophage capable of undergoing the lysogenic cycle without immediately lysing the host (also termed a lysogenic phage, prophage, or inactive phage).

Lysogenic Conversion

The alteration of a host bacterium's phenotype caused by genes carried within an integrated prophage genome.

Induction

The process by which an environmental signal stimulates an integrated viral genome to excise from the host chromosome and transition back to the lytic cycle.

Direct Penetration

A mechanism of viral entry in which capsid proteins attach to the host cell and inject the nucleic acid directly, leaving the empty capsid outside.

Membrane Fusion

An entry method used by enveloped viruses where the viral envelope fuses with the host cytoplasmic membrane, releasing the nucleocapsid into the cell.

Uncoating

The intracellular disassembly and removal of the viral protein capsid to expose the nucleic acid genome.

Positive-Sense Single-Stranded RNA (+ssRNA)

Viral single-stranded RNA that host ribosomes can directly read and immediately translate into viral proteins as mRNA.

Negative-Sense Single-Stranded RNA (-ssRNA)

Viral single-stranded RNA that cannot be translated directly by host ribosomes and must first be transcribed into complementary mRNA.

Retrovirus

A class of RNA viruses, such as HIV, that utilize the enzyme reverse transcriptase to synthesize a DNA copy from their RNA genome.

Budding

The release process of enveloped viruses where virions extrude through the host membrane, gaining an envelope without immediately killing the host cell.

Persistent Infection

A continuous, slow release of virions via budding that allows the host cells to remain alive and shed virus over an extended period.

Latency (Proviruses)

A condition in animal viruses where the viral genome remains dormant inside host cells for prolonged periods or years before reactivating.

Neoplasia

Uncontrolled cell division occurring in a multicellular animal, resulting in a mass of neoplastic cells called a tumor.

Metastasis

The dissemination of malignant cancer cells from their original primary site to distant locations in the body.

Proto-oncogenes

Normal cellular genes that promote cell division and growth; when hyperactivated or mutated, they become cancer-causing oncogenes.

Tumor Suppressor Genes

Cellular genes responsible for repressing cell division; their inactivation eliminates standard controls against uncontrolled cell proliferation.

Viroids

Extremely small, circular single-stranded RNA molecules lacking a capsid that exclusively infect and cause disease in plants.

Prions

Infectious proteinaceous particles that contain no nucleic acids and cause fatal spongiform encephalopathies.

Cellular PrP

The normal, non-pathogenic mammalian protein form characterized primarily by an alpha-helical secondary structure.

Prion PrP

The disease-causing, infectious form of the PrP protein folded predominantly into beta-pleated sheets, which aggregates and forms brain vacuoles.