I. Viruses- A strand of hereditary material covered by protein
A. No nucleus, organelles, or cell membrane
B. So small they need to be seen with an electron microscope
II. How Viruses Multiply
A. Need a host cell
1. Active- attaches to the host cell
hereditary material enters the cell
the viruses hereditary material makes the host cell make virus hereditary material
new viruses form inside the host cell
new viruses are released as the host cell bursts
2. Latent- (dormant) The viruses hereditary material becomes part of the host cell’s hereditary material
When the host cell reproduces, so does the viral DNA
When certain conditions arise the virus becomes active
III How Viruses Affect Organisms
A. Viruses attack all organisms (plants, animals, fungi, protists, prokaryotes)
1. Some viruses can only attack a specific organism
a. example: potato leafroll virus
2. Some viruses can attack multiple organisms
b. examples: rabies, ebola
B. Viruses must fit together exactly on the host cell
C. Bacteriophages- Viruses that attack bacteria
1. attach to the bacteria and inject the hereditary material
2. each virus infected cell releases about 100 viruses
IV. Fighting Viruses
A. Vaccines- created with weakened virus material
1. Edward Jenner made the first one for smallpox
B. Treating Viral Diseases
1. Not antibiotics
2. Body makes interferons
C. Antiviral Drugs
V. Preventing Viral Diseases
A. Vaccinate people
B. Vaccinate animals
C. Improve sanitary conditions
D. Quarantine people
VI. Research with Viruses
A. Gene therapy- using viruses to fix damaged cells