1. Viruses
AKA the things that make us sick!

2. The Virus
Viruses are tiny, non-living particles (NOT cells!) that infect living cells
Cannot reproduce on their own
Do not grow or develop
Do not use energy

3. Parts of a Virus Protein shell called a capsid
genetic material (DNA or RNA)
Envelope made of stolen cell membrane
Glycoproteins that attach to cells (handshake)

4. Parts of a Virus
The virus we looked at yesterday is called a bacteriophage
It has the same structural characteristics, but different names

5. Different Forms of Viruses

6. Viral Replication
Viruses confuse cells, turning them into virus factories:
Virus finds and attaches to a cell by matching glycoprotein receptors (handshake)
DNA or RNA from virus enters the cell

7. Viral Replication
Viral DNA or RNA is copied many times; cell is fooled into reading these new instructions
New viral structures are manufactured
New viruses burst out of the cell, killing it

9. Two Types of Viral Infection
Lytic Infection – virus enters a cell and quickly makes copies, causing lysis of the cell
Lysogenic Infection – a virus “hides” its DNA inside a host cell and lies dormant
Viral DNA is copied each time the cell divides
Will eventually turn lytic

11. The handshakes have to match!
Viral Specificity
Viruses are very specific – infect only certain cells
Ex: cold virus infects respiratory cells
The handshakes have to match!

12. lytic! Example 1 - Influenza
Attacks and kills respiratory cells, causing flu symptoms
Spreads fast, is copied quickly –
lytic!

13. Example 2 - HIV Lysogenic!
Human Immunodeficiency Virus attacks and kills cells of the immune system
Takes years to actually cause illness –
Death of immune cells leads to AIDS (acquired immune deficiency syndrome)
Lysogenic!
Video

14. Vaccines Vaccines are used to give immunity against viral infection
Contain damaged/weakened form of a virus
The immune system can then recognize and destroy the real virus if it ever enters the body
There is no scientific evidence whatsoever that autism is linked to vaccination!