Viruses

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Viruses

• The latin word for poison!!!

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A Virus

• Nonliving particle cosisting of a core of
  hereditary material surrounded by a protein coat-
  protective coat is called the capsid
• Very very small!
• Does not grow
• Does not respond
• Does not eat
• Only reproduces
• Can reproduce only inside a living cell (host
  cell)

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Viruses

• Some can be made into crystals and stored in a
  jar for years.
• If opened, the virus can enter an organism
  (host), quickly reproduce, and cause new
  infections.
• Causes damage to the organism

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Classifying Viruses

• Viruses come in a variety of shapes due to their
  protein covering.
• They are responsible for many diseases.
• They are classified by shape, the kind of
  hereditary material they have, the kind of
  organisms they infect, and their method of
  reproduction.

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Naming Viruses

• Viruses are often named after the disease they
  cause.
• Ex polio viruscauses polio disease
• Also named after the organ or tissue they infect.
• Ex adenovirusinfects the adenoid tissues.

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The T4 Virus

• Also called a bacteriophage
• Type of virus that infects bacteria.
• Many sided head attached to a tail.
• Injects its hereditary material into the cell
  through the tail, much like a hypodermic needle.

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T4 Bacteriophage
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What do viruses do?

• Once inside a host cell, a virus can do 1 of 2
  things.
• 1. Be active (Lytic)
• 2. Be latent or be an inactive part of the
  cell for a while. (Lysogenic)

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The Active Phase (overview)
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The Active Virus (Step 1)
Attach a specific virus attaches to the surface
of a specific bacterial cell.
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The Active Virus (Step 2)
Invade Hereditary material of the virus injects
itself into the bacterial cell.
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The Active Virus (step 3)
Copy Viral heredity material takes control of
the bacterial cell and the cell begins to make
new virus particles.
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The Active Virus (step 4)
Release Cell bursts open and hundreds of new
virus particles are released. New particles go
on to infect other cells.
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The Latent Virus

• The latent virus enters the cell and becomes part
  of the cells hereditary material without
  immediately destroying the cell or making new
  viruses.
• May hide inside cells for many years.
• May become active at any time.

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The Latent Virus (overview)
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Latent Virus (Step 1)
Specific virus attaches to the surface of a
specific bacterial cell. Hereditary mateial of
the virus injects itself into the cell.
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Latent Virus (Step 2)
Virus becomes part of the bacterial cells
chromosomes.
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Latent Virus (Step 3)
Bacterial cell divides.
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Latent Virus (Step 4)
Virus leaves chromosome and becomes active.
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Latent Virus (Step 5)
New viruses are made.
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Latent Virus (Step 6)
Bacterial cell breaks open and releases the
viruses destroying the host bacterial cell.
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Latent Virus Example

• Cold Sore
• From latent phase to the active phase
• Virus enters the cell is remains latent.
• Stress, too much sun or cold makes the virus
  become active.
• Sores become abundant.
• Sores disappear virus becomes latent again.
• Still present, just not active.
• Other examples?

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Viral Diseases

• May cause disease in plants, animals, fungi,
  bacteria, and protists.
• Virulence is used to describe the ability of the
  virus to cause disease
• No antibiotic medications to cure viruses.
• Can be prevented by vaccines.
• Vaccines made from damaged virus (pathogen) that
  can no longer cause disease.

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Vaccine Example

• Edward Jenner
• Developed vaccine in 1796 for smallpox.
• Smallpox was a greatly feared disease.
• Prepared the vaccine from using some of the
  samples taken from the sores of the milkmaids
  that had cowpox.
• Injected the material into healthy people.
• Protected them against the smallpox virus.

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The End