Viruses
Objectives:
•	Understand why acellular
•	Know basic viral anatomy
•	Know stages of 2 life cycles
•	Harmful and beneficial effects
•	Know several examples

General info:
Pathogens (cause diseases) that affect organisms in all 6 kingdoms
Doesn’t belong to any kingdom because they are not considered to be a living organism
Why Acellular (nonliving)?
Viruses:
Don’t grow or carry on metabolism
Do not come directly from other viruses
Lack cytoplasm and organelles
Have only 1 type of nucleic acid (DNA or RNA), cells have both
Have only a few enzymes
Can survive crystallization
Viral Characteristics
All viruses are small; only visible through electron microscope
Consists of two parts:
Nucleic acid core
Can be either DNA or RNA, but never both.
Outer protein coat called a capsid
Capsid
Determines the shape of the virus.
Allows the virus to recognize, bind to and enter specific cells
Highly specific
3 Basic Capsid Shapes:

Geometric shape (e.g. polyhedral)
Ex.  Adenovirus (respiratory virus) or HIV
HIV virus
Helical or rod-shaped
 tobacco mosaic virus
Combined shape
Bacteriophage

Attachment -virus attaches itself to the receptor site of host cell.

3. Replication - The viral nucleic acid is replicated and produces proteins that form the viral enzymes and capsids.

4. Assembly - Viral parts are put together to form new complete viral units.
Lysogenic Cycle (pg 481)
Attachment - Same as Lytic
Injection- Same as Lytic
Cellular Duplication - During normal cell division the viral DNA is also duplicated and passed on with the cell’s own DNA
Harmful Effects of viruses
Cause diseases and disorders
Rabies, mumps, measles, AIDS, chickenpox, shingles, influenza (some), polio, common cold, conjuctivitis (pink eye), warts, hepatitis A, B, & C, mononucleosis, cancer & many more

Beneficial Effects of viruses
Can be used to insert desirable genetic information into cells.
Genetically engineered organisms like tulip coloration
Deliver correct genes into human cells.
Possible antibiotic (kills bacteria)
Combating Viral Infections?
Antiviral Drugs: 
AZT (HIV), Acyclovir (herpes), or Vidarabine (encephalitis) treat the immediate symptoms, but these are not cures.