Biology 11 Viruses

On the fringe of classification… I am not a cell I have no nucleus I can reproduce if the conditions are right I have no metabolism What am I?

Virus Video: http://www.youtube.com/watch?v=UEKS4w9bfJg

Living and not living: Living because: Can reproduce Resemble first forms of life on earth Have evolved Have nucleic acid (DNA, RNA) Movement Can mutate and change

Living and not living: Not-living because: Not cellular No organelles No metabolism No cell membrane or cell wall

Anatomy: Made of genetic material (blue print) surrounded by a protein coat Shapes of viruses vary greatly (spherical, rod-like, cubical, many sided) Example of a virus structure 

Reproduction: Do not grow Must invade a living cell! Can reproduce but only with the help of a host cell (living cell) Viruses are specific and only invade certain types of cells

Stages of reproduction/life cycle: Absorption: virus attaches to host cell Entry: virus injects genetic material into the cell Replication: host cell will produce new virus parts instead of doing its normal work Assembly: new viruses are put together and completed Release: host cell breaks open, new viruses then attach to other cells in the area and the process starts again

Lytic verse Lysogenic: Lytic: a virus life cycle during which a virus takes over a host cell, makes copies of itself and then destroys the host cell Lysogenic: the virus does NOT destroy the host cell. The virus permanently inserts its DNA into the host cell DNA and stays there

Bacteriophage: Is a type of virus that commonly infects bacteria cells.

Characteristics used to classify viruses: 1. Type of nucleic acid: viruses have either single-strand RNA or double-strand DNA, but never both. 2. Physical shape: Viruses are found in several general shapes 3. Envelope : whether or not they have an outer membrane (Gram + or Gram -) 4. Type of host cell: most viruses are very specific about the type of cell they invade. There are specific sites called receptor sites that the viruses attach to on the host cell's surface

Things that viruses cause: Common cold Flu German measles Mumps Chicken Pox Small Pox Cold Sores Herpes Chicken pox Hepatitis Aids West Nile