VirusesChapter 8, Section 4

What are viruses?•Strand of heredity material surrounded by

a protein coating.•Multiplies by making copies of itself with

the help of a host cell•Do not have a nucleus, other organelles or

a cell membrane•Variety of shapes, small•Discovered after the electron microscope

was invented

Active viruses•What are the steps that an active virus

takes to destroy a cell and multiply?•P. 232 chart at the bottom

Latent Viruses•Inactive•After it enters the cell, its hereditary

material becomes part of the cell’s hereditary material.

• It does not immediately make new viruses or destroy the cell.

•Can be latent for many years•Anything can activate it•Cold sore—a latent virus has become

active and starts destroying cells, then becomes latent again

How do they affect organisms?•Animals, plants, fungi, protists, bacteria•Most viruses can infect only specific kinds

of cells---they are limited to one host species or to one type of tissue within a species

•A few viruses affect a broad range of hosts (rabies)

•Cannot move by itself, but can reach the host in several ways: (p. 233 last paragraph)

Treatment and Prevention•Antiviral drugs can help fight, but not

widely used because of side effects•Prevention is best…treatment is very

difficult▫Vaccinations▫Improve sanitary conditions▫Separating patients with diseases▫Controlling animals that spread disease

Natural Immunity•We make interferons

▫Proteins that protect cells from viruses▫Produced rapidly by infected cells and

move to noninfected cells in the hosts.▫This causes the non infected cells to

produce protective substances

Vaccines•Used to prevent disease•Made from weakened virus particles that

cause your body to produce interferons to fight the infections.

•Measles, mumps, smallpox, chicken pox, polio, rabies

•Edward Jenner made first one 1796

Research with Viruses•Gene therapy: (p. 235)•HIV/AIDS

▫Attacks the immune system (protects body from disease)

▫The virus leads to AIDS which allows body to be attacked.

▫No cure▫Research will hopefully help