1. Viruses

2. Virus Facts
Nonliving particle that invade the cells of plants, animals, fungi, and bacteria.
Often destroy the cells they invade
Virology is the study of viruses

3. History of Virology
Wendell Stanley crystallized the tobacco mosaic virus in 1935
Discovered that it may be a chemical rather than a cell

4. Tobacco Mosaic Virus

5. Characteristics No Growth No Homeostasis No Metabolism Can Mutate
May contain DNA or RNA

6. Characteristics Can only reproduce in a host cell
Made up of a nucleic acid core, protein coat, and in some cases an envelope
The coat protects the genetic material
Enables the virus to invade its host cell

8. Virus

9. Viral Shape Determined by capsid or its nucleic acid
Icosahedron-20 triangular faces - herpes simplex, chicken pox, polio
Helix - a coiled spring - rabies, measles, tobacco mosaic virus

10. Icosahedron

11. Helix

12. DNA Viruses
Virus may directly produce DNA that then makes more viral proteins
May join with the host cell’s DNA to direct the synthesis of new viruses
Chicken pox, mono, herpes

13. DNA Viruses

14. RNA Viruses Viral RNA is released into the host cell’s cytoplasm
Uses the host cell’s ribosomes to produce new viral proteins

15. RNA Viruses

16. Retroviruses RNA Viruses
Contains an enzyme called reverse transcriptase.
Uses a template to make DNA

18. Viruses

19. Viroids and Prions
Viroids - smallest known particles that are able to replicate
Consist of a short, single strand of RNA and has no capsid
Disrupt plant cell metabolism and damage crops

20. Viroid

21. Viroids and Prions
Prions - abnormal forms of protein that clump together inside a cell
Clumping kills the cell
Scrapies, Mad Cow

22. Prion

23. Viral Replication

24. Bacteriophage Viruses that infect bacteria
Viral nucleic acid head, a collar, a sheath, which makes up the tail, together making the capsid. There is also a base plate and tail fibers.

26. Animation

27. The Lytic Cycle Destroys the host cell Attachment Entry Replication
Assembly
Release – Released viruses are called progeny

29. Lysogenic Cycle These viruses do not destroy the host immediately
Attachment
Injection
Integration
Cell multiplication

30. Lysogenic

31. Viruses and Human Disease

32. Transmission of Diseases
Human contact
Air
Water
Insect bites

33. Prevention and Treatment
Antiviral drugs
Interfere with viral nucleic acid synthesis
Already infected patients

34. Prevention and Treatment
Vaccination
Inactivated
Do not replicate in a host system
Attenuated
Genetically altered so they are incapable of causing disease

36. Emerging Viruses Newly discovered viruses
Exist in isolated habitats, but infect humans when habitats are developed.
Ebola found in the Democratic Republic of Congo

37. Viruses and Cancer Lysogenic viruses may trigger cancer genes
Hepatitis B
Epstein-Barr

38. More terms to know
Eradication
Lysis
Capsid