Viruses…. Are they alive?

VIRUS Brainpop - Virus A virus is an infectious organism that reproduces within the cells of an infected host. Viruses can only "reproduce" by taking over a cell and using that cell to make new viruses. C. A virus is not "alive" until it enters the cells of a living plant or animal. D. Viruses are NOT living! E. CANNOT carry out life processes unless within a host (living cell). F. After a virus uses a host cell, the host cell is often damaged or destroyed.

I. What is a virus? A. Virus comes from the Latin word for poison. B. Viruses can only be seen with Electron Microscope C. Non-cellular particle made up of genetic material (DNA or RNA) and a protein coat. Not considered to be living things! D. Parasites! CANNOT carry out life processes unless within a host (living cell). Usually host specific- infect only one type of host.

II. Viral Diseases A. Mostly caused by virus destroying cells in body. B. Cause human diseases such as polio, measles, AIDS, and the common cold C. CANNOT be treated with antibiotics D. Best Protection is prevention - Prevented by safe practices or Vaccine if available. (Vaccines must be used before infection begins)

DNA Capsid RNA Capsid Tail fiber Surface proteins Envelope Tobacco Mosaic Virus Influenza Virus T4 Bacteriophage Capsid Tail DNA Tail fiber RNA Capsid Surface proteins Envelope

Measles: also called rubeola, is a highly contagious respiratory infection that's caused by a virus. It causes a total-body skin rash and flu-like symptoms, including a fever, cough, and runny nose.

SARS- flu-like virus that leads to severe pneumonia Brainpop - SARS

Ebola virus- liquification of internal organs and severe bleed out

Zika virus disease is caused by a virus transmitted primarily by mosquitoes. People with Zika virus can have symptoms including mild fever, skin rash, conjunctivitis, muscle and joint pain, or headache. (very similar to the Flu) There is scientific consensus that Zika virus is a cause of microcephaly (birth defect that causes abnormally small and underdeveloped skull and/or brain) and Guillain-Barré syndrome (body's immune system attacks part of the peripheral nervous system). Links to other neurological complications are also being investigated.

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).

Viruses are generally destructive. -Why? 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. How? - 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. Brainpop - AIDS

Brainpop - West Nile Virus 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. Brainpop - West Nile Virus

Attach Release Inject Assemble Copy Figure 19-14 The Lytic Cycle Section 19-3 Bacteriophage protein coat Bacteriophage DNA Release Bacterial chromosome Lytic Cycle Inject Assemble Bacteriophage Bacteriophage DNA Bacteriophage protein Copy Go to Section:

VI. Lysogenic Cycle- When viral DNA becomes part of the cell’s DNA without immediately destroying the cell or making new viruses. A. This is a latent virus; can exist inside host cells for many years. Can become active at any time. Ex- Cold sores.

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

Figure 19-15 A Lysogenic Infection Section 19-3 a) Virus attaches and invades c) Viral DNA separates from Cell’s DNA and becomes active Bacterial chromosome Bacteriophage DNA c) Cell divides Lytic Cycle Lysogenic Cycle e) Cell breaks open and Releases virus Prophage b) Virus’ DNA becomes Part of Cell’s DNA d) New viruses are made Go to Section:

Viruses You may have heard of: Common Cold West Nile Flu Anthrax AIDS Tetanus Bird Flu Tuberculosis Polio Zika Chicken Pox Infectious Mononucelosis Shingles Typhoid Measles Mumps Yellow fever Dengue Fever Rabies