6.2 -Viruses

Warm-up Essential Question What are the characteristics of life? Why can’t we “cure” Viruses?

Viruses Viruses – particle made up of nucleic acid (DNA or RNA), protein, and in some cases lipids that can replicate only by infecting living cells Core of DNA or RNA surrounded by protein coat (capsid), some look like little spaceships

Herpes Herpes virus

Viruses are not alive 1) They do not maintain homeostasis 3) They do not grow. 4) They do not utilize energy on their own. 5) They do not reproduce on their own. 6) They are not made of cells. Although they DO have DNA and RNA

Viruses are TINY http://learn.genetics.utah.edu/content/cells/scale/

Bacteriophage – virus that infects a bacteria

Replicative Cycles Cannot reproduce on own.

C. Lytic Infection 1. Virus enters cell 2. Forces cell to Makes copies of itself 3. Causes cell to burst with new viruses

Lysogenic Infection Review Virus embeds its DNA into the DNA (genome) of the host cell & is replicated along with the host DNA Then after numerous cell divisions acts like lytic infection and bursts cells

Viruses and Disease Examples: polio, rabies, measles, AIDS, mumps, influenza, yellow fever, & common cold

Viruses and Disease Best human protection: vaccines: injection with weakened virus that triggers human immune system to make antibodies. Antibiotics work on BACTERIA because it blocks growth, reproduction, or energy uptake. VIRUSES don’t do those things (has nothing to do with size)

Herpes Simplex ( cold sore) 65% of Americans carry this virus Changing conditions (stress, heat, etc.) can bring about lytic cycle Kiss me, my valentine!!

Iron lung Used for treatment of muscle failure in Polio Can someone scratch my nose?

Model the lytic and lysogenic cycles of a bacteriophage You have a baggie with 4 paperclips, six pieces of pipe cleaner (two big, four small), and a dry erase marker The paperclip is the virus capsid, the pipe cleaners are bacteria DNA and virus DNA/ RNA Using the marker and a whiteboard, draw the bacteria’s cell wall (remember the scale!) You will have to demonstrate to me: Lytic cycle Lysogenic cycle Binary fission Vocabulary words