Summary
Viral replication within a living cell always produces changes in the cell, sometimes resulting in cell death and sometimes slowly killing the infected cells. There are six basic stages in the virus replication cycle: attachment, penetration, uncoating, replication, assembly, and release. A viral infection may be productive, resulting in new virions, or nonproductive, which means that the virus remains inside the cell without producing new virions.
Bacteriophages are viruses that infect bacteria. They have two different modes of replication: the lytic cycle, where the virus replicates and bursts out of the bacteria, and the lysogenic cycle, which involves the incorporation of the viral genome into the bacterial host genome. Animal viruses cause a variety of infections, with some causing chronic symptoms (hepatitis C), some intermittent symptoms (latent viruses such a herpes simplex virus 1), and others that cause very few symptoms, if any (human herpesviruses 6 and 7). Oncogenic viruses in animals have the ability to cause cancer by interfering with the regulation of the host cell cycle. Viruses of plants are responsible for significant economic damage in both agriculture and plants used for ornamentation.
Glossary
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
AZT
anti-HIV drug that inhibits the viral enzyme reverse transcriptase
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
cell necrosis
cell death
chronic infection
describes when the virus persists in the body for a long period of time
cytopathic
causing cell damage
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
horizontal transmission
transmission of a disease between unrelated individuals
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
lytic cycle
type of virus replication in which virions are released through lysis, or bursting, of the cell
lysogenic cycle
type of virus replication in which the viral genome is incorporated into the genome of the host cell
oncogenic virus
virus that has the ability to cause cancer
permissive
cell type that is able to support productive replication of a virus
productive
viral infection that leads to the production of new virions
prophage
phage DNA that is incorporated into the host cell genome
vertical transmission
transmission of disease from parent to offspring