1. DO NOW 1. Label the following as Totipotent, Multipotent, or Pluripotent A.Embryonic Stem Cells B.Bone Marrow Cells C.Umbilical Cord Stem Cells D.Zygote 2. During what embryonic phase do cells differentiate? 3. What is the role of morphogens in embryo development?

2. Viruses Chapter 19.4

3. What to Know about Viruses? 1. Characteristics 2. Structure 3. How they reproduce: ◦ The differences between lytic and lysogenic cycles. 4. How we think they evolved

4. Bacteria vs. Viruses BacteriaVirus Prokaryotic cell Most are free-living (some parasitic) Relatively large size Antibiotics used to kill bacteria Not a living cell (genes packaged in protein shell) Intracellular parasite 1/1000 size of bacteria Vaccines used to prevent viral infection Antiviral treatment

5. Root Words “ phage ” – Virus Host – what the virus infects

6. Virus Characteristics 1. Not made of cells 2. Depend on other hosts (other living things) for life functions, such as reproduction & metabolism 3. Transmit DNA to other organisms 4. Infect all life forms (prokaryotes & eukaryotes) 5. Evolve independently of other organisms 6. Cause most diseases

7. Structure of Virus 1. Nucleic acid : DNA or RNA (double or single- stranded) 2. Capsid : protein shell Some viruses also have viral envelopes that surround capsid bacteriophage

11. Simplified viral replicative cycle

12. VIRAL REPRODUCTION Virulent: active Lysogenic: inactive

13. Bacteriophage Reproduction 1. Lytic Cycle: ◦ Virulent Phage reproduction ◦ Uses host cell to make more of itself ◦ Kills host cell by lysing (rupturing) & releasing new viruses 2. Lysogenic Cycle: ◦ Lysogenic Phage reproduction ◦ Prophage (Viral DNA) is incorporated into host’s DNA and replicated along with it Temperate Phage: uses both methods of replication

14. VIDEO: T4 PHAGE INFECTION T4 PHAGE INFECTIONT4 PHAGE INFECTION

15. Lytic Cycle vs. Lysogenic Cycle

16. Animal viruses have a membranous envelope Host membrane forms around exiting virus Difficult for host immune system to detect virus

17. VIRAL INFECTIONS

18. Bacteriophage Virus that infects bacterial cells

19. Retrovirus reverse transcriptase RNA virus that uses reverse transcriptase (RNA  DNA) Newly made viral DNA inserted into chromosome of host provirus” Host transcribes viral DNA (“provirus”) to make new virus parts Example: HIV (Human Immunodeficiency Virus) Example: HIV (Human Immunodeficiency Virus)

20. HIV ◦ Infects white blood cells ◦ HIV+: provirus (DNA inserted) ◦ AIDS: active viral reproduction

21. VIDEO: HIV LIFE CYCLE HIV LIFE CYCLEHIV LIFE CYCLE

22. HIV = Retrovirus

23. Herpes virus Smallpox Herpes Simplex Virus 1 (HSV-1) Herpes Simplex Virus 2 (HSV-2) Eradicated in 1979 due to worldwide vaccination campaigns

24. VACCINES

25. Vaccines Consists of a weakened virus or part of pathogen that triggers immune system response

26. Emerging viruses = mutation of existing viruses

27. Prions Misfolded, infectious proteins that cause misfolding of normal proteins Eg. mad cow disease (BSE),Creutzfeldt- Jakob disease (humans), scrapie (sheep)

28. VIRUS EVOLUTION Where did they come from?

29. Viral Evolution Viruses evolved many times from many different cell (host) groups 1)Some are probably derived from escaped genetic materials 2)Some probably evolved from highly reduced parasites

30. EXIT QUIZ 1. What are the 2 common parts that all viruses have? 2. What is the overall outcome of a Lysogenic Cycle? 3. What is the overall outcome of a Lytic Cycle? 4. Why do people have to get a flu shot every year?

31. Viroids Small, circular RNA molecules that infect plants Cause errors in regulatory systems that control plant growth Eg. coconut palms in Philippines

32. Diseases caused by prions Prions act slowly – incubation period of at least 10 years before symptoms develop Prions are virtually indestructible (cannot be denatured by heating) No known cure for prion diseases