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  1. http://www.cellsalive.com/howbig.htm

  2. Ch 18 Microbial Models: Genetics of Viruses and Bacteria

  3. smaller than ribosomes!

  4. S.A.R.S. HIV Ebola Polio Bird Flu Meningitis chicken pox

  5. Virus- *biological particle(not a cell) *composed of nucleic acid (RNA or DNA)

  6. Virus- *surrounded bycapsid(protein coat)and sometimes aviralenvelope(membrane surrounding)

  7. The head of a dress-maker's pin can provide seating accommodation for fivehundredmillion rhinoviruses (cause of the common cold) !

  8. Why not alive? • Lacks: nucleus, cytoplasm, organelles, cell membrane

  9. Why not alive? • No reproduction by mitosis No meiosis (require a host cell in order to reproduce) obligateintracellularparasites

  10. Why not alive? • Resistant to alcohol resistant to dehydration by osmosis obligateintracellularparasites

  11. Why not alive? • virus crystallization cells cannot form crystals obligateintracellularparasites

  12. Reproduction: 3 ways:

  13. Lytic Cycle

  14. Lytic Cycle “lock & key”

  15. Lytic Cycle phage injects DNA (hopefully, forthevirus, it is resistant to the restriction nucleases!)

  16. Lytic Cycle phage DNA hydrolysises bacterial DNA via. enzymes

  17. Lytic Cycle phage proteins are produced, phage DNA reproduced

  18. Lytic Cycle host cell provides: nucleotides, ribosomes, tRNA etc.

  19. Lytic Cycle Lysozyme produced and bacterial wall is digested

  20. Lytic Cycle BOOM!!

  21. Lytic Cycle virulent virus

  22. Lysogenic Cycle

  23. Lysogenic Cycletemperate viruses

  24. Lysogenic Cycle “phage” inserts DNA; via. “lock & key”

  25. Lysogenic Cycle  encorporate into bacterial DNA via. crossing over

  26. Lysogenic Cycle cellular division w/ a “friend” -replicates along with bacterial DNA)

  27. Lysogenic Cycle at some point,  exits the chromosome, & initiates a LYTIC cycle

  28. Lysogenic CyclePhages manufactured BOOM!!

  29. latent/ temperate virulent

  30. Why haven’t phages exterminated all bacteria? • Restriction Enzymes in bacteria • Methylation of bacterial DNA prevents the restriction enzyme from attacking its own self

  31. Why haven’t phages exterminated all bacteria? • Natural Selection favors the mutant bacteria w/ protein receptors that have an altered shape • no longer recognizable by phage

  32. Why haven’t phages exterminated all bacteria? • LYSOGENY

  33. variations of viral reproduction

  34. Viruses are Classified as: 1. DNA viruses 2. RNA viruses

  35. Viruses are Classified as: 1. membranous envelope present 2. membranous envelope absent

  36. ex.of enveloped = herpes virus Reproduce in nucleus Envelope derived from nuclear membrane Typically, leave some DNA behind in nerve cells

  37. ex. Herpes Simplex Type 1 (cold sore)

  38. Herpes Viruses • Use nuclear membrane to derive new envelope. • Viral DNA integrated into Host DNA as a provirus. • Shows both lytic and lysogenic life cycles.

  39.  does not kill host  Viral Envelope   

  40. RETROVIRUS ex. HIV

  41. human immunodificiency virus

  42.    HIV ` host is a WBC called a T-cell

  43. http://www.youtube.com/watch?v=B7ITZgag6w0&feature=related http://www.youtube.com/watch?v=dyxujBKHdWc http://www.youtube.com/watch?v=9leO28ydyfU&NR=1

  44. HIV needs to connect to TWO protein types on the outside of the Immune System’s Helper T Cells

  45. HIV needs to connect to TWO protein types on the outside of the Immune System’s Helper T Cells (WBC)

  46. LAST KIND • DNA

  47. DNA Viruses 1.Insert their DNA into host/ the host produces mRNA compliment 2.Production of new viral proteins, or join with the DNA of the host cell  3.Directs production of new viruses

  48. viral DNA replicated uses it to enter host DNA capsid removed genetic material duplicated