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VIRUSES
What kingdom are viruses found
in?______________________
none
Are they living or non-living? Explain.
Non-living because they require a
host to reproduce
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Some general information about viruses
A Typical Virus
•All viruses are ____________
and therefore require a
nonliving
host organism for its survival and continued
reproduction.
host range
•Viruses only infect in their ___________________.
•Viruses that infect bacteria are called
capsid
DNA
____________________.
bacteriophage or phage
•All viruses act by forcing the host cell to manufacture
100’s or 1000’s of copies of itself. While this is going on,
the host cell can’t make the material it needs to carry
sheath
out its normal function – an _____________
infection results. If
the infection spread locally an _____________ occurs,
andepidemic
if it travels globally it creates a ___________ .
•Some viruses
contain RNA instead of DNA. RNA viruses
pandemic
cause the more serious diseases.
tail
•Ex: DNA virus diseases_______________________
hepatitis B, cold sores, chicken
pox, tumours, etc.
•Ex. RNA virus diseases _______________________
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measles, mumps, polio, the
cold, HIV, rabies
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Phage reproduce either one of two ways:
Lytic Cycle - the virus ___________________________________________________
completely destroys the host cell
Lysogenic Cycle - the virus ___________________________________________
does not immediately destroy the host cell, virus enters a
dormant state
lysis
TYPE A: Lytic Cycle - the host cell is completely destroyed (________________)
- reproduction can occur rapidly (_________________)
< 1 hour
entire virus
- In animal cells the _______________
enters the host
1. Phage attaches itself to host cell
2. Phage injects its DNA into the host
3. Phage DNA instructs host to make
more phage DNA and capsids
4. New phage are assembled inside
the host cell
5. Host cell fills with phage and fluid
and bursts = lysis
6. Several hundred new phage are
released and seek out uninfected
cells
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TYPE B: Lysogenic Cycle - the host cell is not destroyed (lysed) immediately
- viral DNA remains dormant inside host cell
months to years
- In animals, the entire virus remains dormant in the host cell for _______________
Ex. ______________________.
Herpes, HIV
1. Phage attaches to host cell
and injects DNA
2. Phage DNA becomes part
of host cell’s DNA by
recombination
3. Host cell reproduces
normally and copies the
phage DNA
4. Eventually phage DNA
breaks away and instructs
the cell to make new
phage DNA and capsid
5. New phage form, cell
lyses, phage are released.
Review 
Define: Vaccination, Transduction, types of Gene Therapy, Viroids, Prions, BSE, CJD.
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