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AKA the things that make us sick! 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 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) Parts of a Virus The virus we looked at yesterday is called a bacteriophage It has the same structural characteristics, but different names Different Forms of Viruses Viral Replication Viruses confuse cells, turning them into virus factories: 1. 2. Virus finds and attaches to a cell by matching glycoprotein receptors (handshake) DNA or RNA from virus enters the cell Viral Replication 3. Viral DNA or RNA is copied many times; cell is fooled into reading these new instructions 4. New viral structures are manufactured 5. New viruses burst out of the cell, killing it Two Types of Viral Infection 1. 2. 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 Viral Specificity Viruses are very specific – infect only certain cells › Ex: cold virus infects respiratory cells The handshakes have to match! Example 1 - Influenza Attacks and kills respiratory cells, causing flu symptoms Spreads fast, is copied quickly – lytic! Example 2 - HIV Human Immunodeficiency Virus attacks and kills cells of the immune system Takes years to actually cause illness – Lysogenic! Death of immune cells leads to AIDS (acquired immune deficiency syndrome) Video 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!