1. Chapter 18.2 Viruses and Prions
“Viruses and prions are smaller and less complex than bacteria; they invade cells and can alter cellular functions.”

2. Chapter 18.2 Learning Targets
Illustrate the general structure of viruses.
Compare and contrast the sequence of events in viral replication by the lytic cycle, the lyosgenic cycle, and retroviral replication.
Discuss the structure, replication, and action of prions in relationship to causing disease.

3. T-4 Virus - infects E. coli
Characteristics
non-living particles
invade living cells
pathogenic - named after the disease they cause or organ they infect
smallest of all organisms
T-4 Virus - infects E. coli

5. VIRUS - an obligate intracellular parasite
INFECTIOUS MONONUCLEOSIS

6. Wendell Stanley (1904 - 1971) first isolated TMV in 1935.
Origin of Viruses
Wendell Stanley ( ) first isolated TMV in 1935.
Viruses may have originated from host cells
first seen by an electron microscope
Tobacco mosaic virus - first virus discovered

7. 1886 - “Living Fluid Infectant” - the virus passed through filters that held bacteria.

8. Viral Structure Inner core - contains viral DNA or RNA (never both)
Capsid - outer coat of protein
Envelope - outer layer on larger viruses

9. Various Shapes of Viruses

10. Viral Replication Lytic Cycle
1. Attachment
2. Injection
3. Replication
4. Assembly
5. Lysis

11. LYSOGENIC CYCLE 1. Attachment 2. Injection
Viral DNA integration (provirus)
4. Cell division
5. Replication
6. Assembly
7. Lysis

12. L Y S O G E N I C L Y T I C

13. Viruses Bozeman Biology
8:06 min.

14. VIRUSES CHAPTER 18
Part 2

15. Edward Jenner - discovered a vaccine for smallpox

16. Smallpox Variola (Major & Minor)
First virus to be studied in detail
Edward Jenner
First vaccine - cowpox virus (vaccinia virus)

17. Child with smallpox

18. (Ali Maow of Merka, Somalia, contracted smallpox in 1977 at the age of 23. His was the last known case of smallpox in the world.)
Last case of smallpox

19. Icosahedral Virus (many sides)
Wart virus
Polio - Naked, small, icosahedral virus

20. Enveloped Virus
INFLUENZA VIRUS

21. Children with measles (uncommon today)

22. BACTERIOPHAGE
E-Coli Bacteria

23. Attachment of a phage to the cell wall of E-Coli

24. Temperate vs. Virulent Viruses

25. HERPES ZOSTER (“Shingles”)

26. HERPES VIRUS
HERPES

27. Retroviruses RNA viruses
Reverse transcriptase makes DNA from its RNA
Includes HIV, polio & some cancers
HIV

28. Retrovirus Cycle

29. The Immune System Bozeman Biology
13:47 min.

30. HIV / AIDS

32. When HIV Becomes AIDS (HIV #2)
3:56 min

33. Louis Pasteur - discovered a vaccine for rabies

34. PATHWAY OF
RABIES
VIRUS

35. Animal Rabies in U. S. 1999