The Amazing World of Viruses

1. The Amazing World of Viruses

2. Viral History 2

3. Discovery of Viruses Beijerinck (1897) coined the Latin name “virus” meaning poison He studied filtered plant juices & found they caused healthy plants to become sick 3

4. Tobacco Mosaic Virus Wendell Stanley (1935) crystallized sap from sick tobacco plants He discovered viruses were made of nucleic acid and protein 4

5. Smallpox Edward Jenner (1796) developed a smallpox vaccine using milder cowpox viruses Deadly viruses are said to be virulent Smallpox has been eradicated in the world today 5

6. Viewing Viruses Viruses are smaller than the smallest cell Measured in nanometers Viruses couldn’t be seen until the electron microscope was invented in the 20th century 6

7. Interdependence Viruses and organisms relyon their environmentand other species for survival.

8. Viruses • But, Viruses are NOT cells. • A virus is an infectious agent made up of: • a core of nucleic acid (RNA or DNA) • a protein coat

9. Alive or not? Even scientists disagree as to whether or not viruses are alive. What do you think? Look at the chart on the next page to help you decide.

10. Characteristic of life

11. Alive or not? Most scientists do not consider viruses to be living because don’t have the necessary parts to reproduce on their own. They MUST infect a cell and use its parts to reproduce.

12. Because viruses don’t carry around the necessary parts to reproduce themselves they are very simple structures. Structureof a virus ENVELOPE NUCLEIC ACID CAPSID

13. Consists of 2 parts: A Nucleic acid -either DNA or RNA Capsid – A protein Coat that surrounds and protects the DNA/RNA Structureof a virus ENVELOPE NUCLEIC ACID CAPSID

15. Standard DNA based Virus Retro Virus Bacteriophage Types of Viruses

16. A strand of nucleic acid surrounded by a protein coat. DNA  RNA  Protein Basic Virus

17. A virus that contains RNA instead of DNA Human Immunodeficiency Virus (HIV) is a retrovirus HIV causes AIDS Retrovirus CAPSID ENVELOPE RNA

19. A virus that infects only bacteria. Bacteriophage CAPSID HEAD DNA CAPSID TAIL FIBER

21. Helical Viruses 21

22. Polyhedral Viruses 22

23. Complex Viruses 23

24. 24

25. Ticking time bombs . . . Viruses CANNOT reproduce, EXCEPT inside a living cell. They invade a living cell and let the cell work for them.

26. Virus Cycle • A Viral Infection has 2 possible stages: • Lytic Cycle • Lysogenic Cycle • *Some viruses go straight to the lytic phase and never enter the lysogenic phase

27. Virus Cycle • Lytic Cycle - stage where virus is actively reproducing and killing host cells • Lysogenic Cycle - stage where virus is inactive and host cells remain unharmed

28. Lytic Cycle • The virus injects its DNA into the host cell • The DNA uses the host cell’s resources and organelles to make new viruses. • The viruses cause the cell to burst • The cell dies and the newly made copies of the virus are released to go infect new cells. • The cycle continues.

29. Cycle Illustration 1 2 3 4 5

30. Lysogenic Cycle • The Virus injects its DNA into the host cell. • The DNA inserts itself into the host cell’s DNA and stays there inactive. • There are NO symptoms of the infection at this stage. • Eventually the viral DNA will remove itself from the host cell’s DNA and the lytic cycle will begin.

31. Lyso- Genic Cycle Lytic Cycle

32. All viruses are parasites: they benefit while harming the host cell/organism. Viruses cause disease in every kind of organism—animals, plants, fungi, protists, and bacteria. Role of viruses

33. Viral diseases • Are hard to cure, but many can be prevented by • Good hygiene • Immunization

34. HIV Measles Smallpox Influenza Chicken pox Common cold Herpes Warts Mononucleosis Mumps Some viral diseases

36. MEASLES

37. Mumps

38. SMALLPOX

39. HERPES

40. 1918 Flu

41. Herpes Virus SIMPLEX I and II 41

42. Adenovirus COMMON COLD 42

43. Influenza Virus 43

44. Chickenpox Virus 44

45. Papillomavirus – Warts! 45

46. Helical Viruses 46

47. Polyhedral Viruses 47

48. Complex Viruses 48

50. Links http://www.virology.net/Big_Virology/BVFamilyIndex.html