Download Viruses Notes

Viruses Notes
What is a virus?
•A virus is: an infectious ___________________ consisting of nucleic acid enclosed in a
protein coat.
What Kingdom do viruses belong to?
•None! That’s a trick question.
•___________________ are non-living!!!
•They are simply nucleic acids wrapped in protein.
Viral size
•Their size is VERY ___________________! Smaller than a ribosome (the smallest have
only 4 genes)!
Bacteriophages
•They are viruses that infect ___________________ such as E. coli
Reproduction
•A virus MUST ___________________ a cell and take over the cell’s metabolic
machinery to reproduce. An isolated virus is unable to do ANYTHING without a
___________________ cell.
Viruses:
•lack enzymes for metabolism
•have no ___________________ for protein production.
•they are simply packaged genes in transit from one host cell to another.
•are specific in the types of host cells they can ___________________ (Ex: rabies infects
mammals, swine flu infects pigs and humans, small pox infects humans)
•of eukaryotes are tissue-specific (Ex: cold viruses infect upper respiratory tract, AIDS
infects white blood cells, polio infects nerve cells).
Lytic Cycle
•(examples colds, mumps, rabies)
•tail fibers attach to cell virus injects DNA into cell
•viral DNA takes over the cell’s DNA
•host cell is reprogrammed to copy the viral genes
•new ___________________ assemble around new viral DNA to form new viral
particles
•new viral particles released; cell is destroyed
A.I.M.A.R.
•A- ___________________
•I- ___________________
•M-___________________
•A- ___________________
•R- ___________________
Lysogenic Cycle
•examples are herpes, cold sores, HIV, chicken pox
•tail fibers ___________________ to cell
•virus injects DNA
•viral DNA becomes part of cell ___________________ (this is a provirus; no
interference w/normal cell function
•Provirus is replicated along with host cell’s DNA
•Can remain in this stage for years! May enter lytic stage when conditions are favorable
(changes in temp., food, stress, etc.)
Retroviruses
•___________________ contain RNA rather than DNA; they cause the cell to produce a
DNA copy of their RNA genes and this DNA is inserted into the DNA of the host cell.
___________________ is an example of a retrovirus.