Viruses :Tiny Biological Particles Size video

Viruses are abiotic  Do not meet all 5 characteristics of living things….  1) can not obtain energy  a) do not exchange gasses  b) do not take in nutrients/water  2) can not reproduce on own  a) host cell makes the copies of viruses  3) viruses are not cells

Viruses composed of:  1) Protein covering  2) Nucleic Acid either…  a) DNA (deoxyribonucleic acid)  b) RNA (ribonucleic acid)  ** no water

Host cells  Cells that have been invaded by viruses or virus DNA/RNA  Host cell is forced to make virus DNA/RNA  Host cell is forced to make virus proteins  These parts are assembled in the host cell to create new virus particles

2 methods of viral attack  1) lytic cycle: immediate take over of cell  a) destruction of host cells cause disease symptoms  2) lysogenic cycle: covert attack  a) virus DNA blends in with host cell DNA  b) when host cell divides the virus divides too  c) stress or illness cause virus to switch to lytic cycle and cause disease symptoms

 1) Attachment – virus finds host & locks on  2) Penetration- entire virus or virus DNA/RNA enters host cell  3) Replication & protein synthesis of Viral genes makes viral proteins and DNA/RNA  4)Assembly – new viruses put together  5) Release – new viruses leave host cell Viral Multiplication Steps

 Steps proceed rapidly and end in lysing of cell Lytic pathway

Lytic cycle examples  1) Rhino virus…  common cold  2) Influenza virus…  flue virus

 1) Viral DNA becomes part of host DNA  2) Viral DNA copied each time host cell divides  3) Latent period = no symptoms but  more and more host cells are becoming infected  4) Stimulus causes switch to lytic cycle and symptoms appear Lysogenic Pathway

Lysogenic cycle examples  Herpes simplex I …  cold sores  Varicella…..  chicken pox (lytic) shingles (lysogenic)

Viruses we get immunized against  Measles  Mumps  Chicken pox can be fatal in adults  influenza

Vaccinations  Activate our acquired immune system   Cause creation of memory cells  Prevent us from showing symptoms of disease even if we are exposed to it  Prevent us from transmitting disease to others  Can eradicate disease causing agents from the face of the earth!

Smallpox virus  wiped off the face of the earth, except for samples held in labs in the U. S. & Russia  scientists declared world small pox free in  U.S. hasn't vaccinated for smallpox since  1 OR 2 PEOPLE IN 1 MILLION vaccinated may die because this is a LIVE VACCINE of a pox similar to small pox ( %)  fears remain about the smallpox samples being used as bioweapons.

How we make vaccinations  Viruses identified & isolated from host  Host cells found in which viruses can reproduce ( eggs, tissue culture)  millions of viruses are produced  Viruses are purified  Viruses are either killed or weakened  8, _ ,00.html 8, _ ,00.html

Live Attenuated vaccinations  living microbes weakened = no symptoms.  closest to natural infection, so strong immune responses  often confer lifelong immunity  The remote possibility that attenuated microbes could mutate back to disease causing

 Between 1990 and 1995 in the UK,  % of cases. Only a tiny number of those were serious.

Inactivated Vaccinations  Produced by killing the virus with chemicals, heat, or radiation.  More stable  Dead microbes can’t mutate  Stimulate weaker immune response  booster shots needed

Subunit Vaccines  include only parts of virus protein  Much lower chances of reactions

 Chances are you don’t know anyone who has had diphtheria, whooping cough (pertussis), measles, mumps, or German measles (rubella).  In the 19th and early 20th centuries, these illnesses struck hundreds of thousands of people in the U. S. each year, mostly children, and tens of thousands of people died.  Now vaccinations have all but wiped them out

Different infectious agents 