test 2 ch 16 Flashcards
a small, infectious agent that is genetic information enclosed in a protein coat
virus
two characteristics that all viruses share
genetic information and a protein coat
surround the genetic material of a virus, the shape determines a virus’s overall form
protein coat (capsid)
t or f: all viruses contain genetic material that carries the recipes for their proteins
true
a lipid and protein-rich outer layer derived from the host cell’s membrane, proteins embedded in this outer layer help a virus invade a new host cell
viral envelope
viruses that infect bacteria
bacteriophage
the types of organisms or cells that a virus can infect
host range
the host of a virus that acts as a continual source of viral infection for other host species (examples are wild birds, rodents, mosquitoes, raccoons)
viral reservoir
why do biologists not consider viruses alive?
because they do not metabolize, respond to stimuli, or reproduce on their own
t or f: viruses evolve by natural selection
true
attachment (virus adheres to host cell receptor), penetration (virus enters cell), synthesis (multiple copies of the viral genome and proteins are produced by the host cell), assembly (the viral genetic info. is packaged in protein coat), release (new viruses leave host cell)
five steps of viral replication
in this cycle a virus enters a bacterium, immediately replicates, and causes the host cell to birth as it releases a flood of new viruses; the newly released viruses infect other bacteria, repeating until all cells are dead
lytic cycle
in this cycle, the genetic material of a virus is replicated along with the bacterial chromosome, but the cell lives and reproduces as usual, at some point the virus will revert to the other cycle
lysogenic cycle
the DNA of a lysogenic bacteriophage that is inserted into the host chromosome
prophage
describes the ability of a virus to damage its host during an infection, the more virulence the most likely to cause dire illness or death
virulence
symptoms of a viral infection in animals using influenza as the example
cough and sore throat
human immune system’s response to viral infection (influenza) that help to battle the virus
fever and body aches and fatigue
viral genetic information inside an animal cell lies dormant; even as the infected host cell divides, new viruses are not produced bu the virus may be reactivated later (examples; cancer or papillomavirus ; or epstein-barr virus)
latent infection
“teaches” the immune system to recognize one or more molecular components of a virus without actually exposing the person to the disease
vaccine
how do viruses spread within a plant
viruses multiply at the initial site of infection, the killed plant cells often appear as small dead spots on the leaves; over time the viruses can spread from cell to cell through plasmodesmata, can also move throughout a plant by entering vascular tissues that distribute sap
symptoms of viral infections in plants
streaking of some flower petals or blotchy, mottled leaves or abnormal growth
how do plants fight viral infections
virus-infected cells may “commit suicide” before the infection has a chance to spread to neighboring cells or the plant may destroy the mRNA transcribed from viral genes
a highly wound circle of RNA that lacks a protein coat; naked RNA that can infect a plant cell and can infect a plant by using its RNA to interfere with the plant’s ability to produce one or more essential proteins
viroid
infectious particle made of protein; PrP is the normal membrane protein that can exist in multiple 3D shapes, at least one of which is abnormal and can cause disease
prion protein
define prion
proteinaceous infectious particle
diseases caused by prions
mad cow disease, kuru (associated with cannibalism in humans)
