General Virology

Flashcards covering key vocabulary from a lecture on general virology, including virus structure, replication, and classification.

Viruses

Minute microorganisms, ranging from about 15-20 nm to 250 nm. Obligatory intracellular. Not able to carry out individual metabolic activity. Replication is assembly of sub particles. Viral genome consists of only one type of nucleic acid (RNA or DNA).

Virion

The extracellular form of a virus, an inert particle outside the cell that cannot propagate in the environment. It consists of the viral genome (nucleic acid) enwrapped with a protein coat called a capsid.

Capsid

Protein coat that enwraps the viral nucleic acid. It is composed of identical protein subunits called capsomeres.

Nucleocapsid

Complex formed when viral capsid proteins are bound tightly to genomic nucleic acid.

Enveloped Viruses

Viruses that carry an additional outer lipid membrane or envelope, usually obtained from the cytoplasmic membrane of the host cell.

Naked (Simplex) Viruses

Viruses that contain the capsid as the only external coat.

Quasispecies

A total number of closely related genetic variants arisen from intensive mutations of primary virus (“mutant cloud”) in the course of individual viral infection; typical for fast propagating RNA-containing viruses with error-prone replication.

Host Range

Refers to what organisms a virus can infect.

Tissue Tropism

The limitation of many viruses to only infect certain cell types or tissues within a multicellular plant or animal.

Satellite Viruses

Viruses which require a second (helper) virus for replication (e.g., hepatitis delta virus requires hepatitis B).

Viroids

Small, autonomously replicating molecules; single-stranded circular RNA, 240-375 residues in length; plant pathogens.

Prions

Infectious protein molecules responsible for transmissible and familial spongiform encephalopathies (e.g., Creutzfeldt-Jakob disease); pathogenic prion protein Prpsc formed from normal human protein, PrPc, through post-translational processing.

Lytic Cycle

A viral replication cycle resulting in the lysis and death of the host cell.

Lysogenic Cycle

A viral replication cycle where the viral DNA integrates into the host chromosome and can remain dormant for an extended period.

Horizontal Viral Transmission

Transmission of a virus via respiratory tract, intestinal tract, abrasions/wounds or the genital tract.

Vertical Viral Transmission

Transmission of a virus from mother to fetus via the placenta or mother to baby via milk.

Cytopathic Effect

The changes in cell morphology and viability resulting from viral action during cultivation in cell cultures; includes degeneration, destruction of monolayer, cell lysis, plaque appearance, inclusion formation, cytoplasmic vacuolization, symplast, syncytium, and giant cell formation.