Key Terms

acellular

lacking cells

acute disease

disease where the symptoms rise and fall within a short period of time

asymptomatic disease

disease where there are no symptoms and the individual is unaware of being infected unless lab tests are performed

attenuation

weakening of a virus during vaccine development

AZT

anti-HIV drug that inhibits the viral enzyme reverse transcriptase

back mutation

when a live virus vaccine reverts back to it disease-causing phenotype

bacteriophage

virus that infects bacteria

budding

method of exit from the cell used in certain animal viruses, where virions leave the cell individually by capturing a piece of the host plasma membrane

capsid

protein coating of the viral core

capsomere

protein subunit that makes up the capsid

cell necrosis

cell death

chronic infection

describes when the virus persists in the body for a long period of time

cytopathic

causing cell damage

envelope

lipid bilayer that envelopes some viruses

fusion

method of entry by some enveloped viruses, where the viral envelope fuses with the plasma membrane of the host cell

gall

appearance of a plant tumor

gene therapy

treatment of genetic disease by adding genes, using viruses to carry the new genes inside the cell

group I virus

virus with a dsDNA genome

group II virus

virus with a ssDNA genome

group III virus

virus with a dsRNA genome

group IV virus

virus with a ssRNA genome with positive polarity

group V virus

virus with a ssRNA genome with negative polarity

group VI virus

virus with a ssRNA genomes converted into dsDNA by reverse transcriptase

group VII virus

virus with a single-stranded mRNA converted into dsDNA for genome replication

horizontal transmission

transmission of a disease from parent to offspring

hyperplasia

abnormally high cell growth and division

hypoplasia

abnormally low cell growth and division

intermittent symptom

symptom that occurs periodically

latency

virus that remains in the body for a long period of time but only causes intermittent symptoms

lysis

bursting of a cell

lysogenic cycle

type of virus replication in which the viral genome is incorporated into the genome of the host cell

lytic cycle

type of virus replication in which virions are released through lysis, or bursting, of the cell

matrix protein

envelope protein that stabilizes the envelope and often plays a role in the assembly of progeny virions

negative polarity

ssRNA viruses with genomes complementary to their mRNA

oncogenic virus

virus that has the ability to cause cancer

oncolytic virus

virus engineered to specifically infect and kill cancer cells

pathogen

agent with the ability to cause disease

permissive

cell type that is able to support productive replication of a virus

phage therapy

treatment of bacterial diseases using bacteriophages specific to a particular bacterium

positive polarity

ssRNA virus with a genome that contains the same base sequences and codons found in their mRNA

prion

infectious particle that consists of proteins that replicate without DNA or RNA

productive

viral infection that leads to the production of new virions

prophage

phage DNA that is incorporated into the host cell genome

PrP^c

normal prion protein

PrP^sc

infectious form of a prion protein

replicative intermediate

dsRNA intermediate made in the process of copying genomic RNA

retrovirus

virus with an RNA genome that must be reverse transcribed into DNA before being incorporated into the host cell genome

reverse transcriptase

enzyme found in Baltimore groups VI and VII that converts single-stranded RNA into double-stranded DNA

vaccine

weakened solution of virus components, viruses, or other agents that produce an immune response

vertical transmission

transmission of disease from parent to offspring

viral receptor

glycoprotein used to attach a virus to host cells via molecules on the cell

virion

individual virus particle outside a host cell

viroid

plant pathogen that produces only a single, specific RNA

virus core

contains the virus genome