Viruses

Viruses are not a type of bacteria! Virus comes from the Latin word for poison. Viruses are so small they can only be seen with Electron Microscope. Bacteria and other cells are large enough to be seen with a light microscope.

Not considered to be a living thing because they are non-cellular particle. They are only made up of genetic material (DNA or RNA) and a protein coat. Parasites! CANNOT carry out life processes unless within a host (living cell). Usually host specific- infect only one type of host.

T4 Bacteriophage Tobacco Mosaic Virus Influenza Virus Protein Tail DNA Tail fiber RNA Protein Surface proteins Envelope RNA Protein Section 19-3 Figure Virus Structures Go to Section: Infects: bacteria Infects: plants Infects: Animals Viruses infect a variety of different organisms and come in many different shapes

Viral Diseases Mostly caused by virus destroying cells in body. Cause human diseases such as polio, measles, AIDS, and the common cold

Viruses are generally destructive. Virus has to be inside a living cell to reproduce. The cell that it reproduces in is a host cell. A virus destroys its host cell.

Lytic Cycle -how a virus reproduces When a virus enters a cell and is active it causes the cell to make new viruses. This will eventually destroy the host cell.

Steps of Lytic Cycle 1. Attach-virus attaches to the surface of a cell 2. Inject- the hereditary material of the virus injects itself into the cell. 3. Copy-the viral DNA takes control of the cell and the cell begins to make new virus particles. 4. Assembles- viral particle are assembled into new viruses 5. Release-the cell bursts open and hundreds of new virus particles are released. These new virus particles go on to infect other cells.

Bacteriophage Bacteriophage DNA Bacteriophage protein BacteriophageDNA Bacterial DNA Lytic Cycle Section 19-3 Figure The Lytic Cycle Go to Section: Attach Inject Copy Release Assemble

Latent Viruses- (Dormant Virus) Do not immediately enter the lytic cycle. The viral DNA becomes part of the cell’s DNA without immediately destroying the cell or making new viruses. A latent virus can exist inside host cells for many years. Can become active at any time. Ex- Cold sores.

Viral Diseases CANNOT be treated with antibiotics Best Protection is prevention - Prevented by safe practices or Vaccine if available. (Vaccines must be used before infection begins)

Franklin D Roosevelt

Rabies

SARS- flu-like virus that leads to severe pneumonia

Ebola virus- liquification of internal organs and severe bleed out

III. Kinds of Viruses A. Viruses are classified by their shape, the kind of hereditary material they contain, organism that they infect and reproduction. B. The protein that covers a virus gives it its shape. C. Viruses are often named for the disease that they cause (Polio) or the organ or tissue that they infect (SARS).

VII. Steps of Lysogenic cycle 1. Virus attaches to the cell and injects hereditary material into the cell. 2. Virus becomes part of the cell’s DNA. 3. Cell divides, creating viral DNA along with its own DNA. 4. This can happen for years until virus becomes active 5. Then it will enter the lytic cycle

Bacteriophage DNA Bacterial chromosome Prophage Lytic Cycle Lysogenic Cycle Section 19-3 Figure A Lysogenic Infection Go to Section: a) Virus attaches and invades b) Virus’ DNA becomes Part of Cell’s DNA c) Cell divides c) Viral DNA separates from Cell’s DNA and becomes active d) New viruses are made e) Cell breaks open and Releases virus

Bovine Spongiform Encephalopathy Mad Cow Disease

VIII. Prions- no genetic material (DNA nor RNA) only protein which infects the nervous tissue of the brain (scientists think they cause Mad Cow Disease).

Finding the host: Outbreak!