1. Viruses

2. Learning Goals 1)Understand the structure of a virus 2)Provide support evidence to answer the question, “Are viruses living?” 3)Explain the two (2) ways that viruses can reproduce 4)Describe both the benefits and negative aspects of viruses

3. Viruses: Are They Living?? Viruses are NOT LIVING organisms  they cannot reproduce on their own and are not made of cells Viruses are similar to living things in the following ways: Use DNA and RNA to store genetic information Adapt to changing conditions by genetically mutating (can avoid destruction by medicine) Viruses are made of proteins and nucleic acids

4. Viruses: How Are They Negative?? Viruses can’t be killed with antibiotics. Some viruses can kill or cause disease: chicken pox Polio Colds Influenza Rabies AIDS Measles some cancers even

5. Viruses: Structure and Function Viruses are composed of: Inner nucleic acid (DNA or RNA) DNA/RNA surrounded by an outer protective protein coat called a capsid (acts like a key to a door  unlocks entryway into host cell and how it is identified by immune system) Example: HIV virus only infect T cells  avian flue virus can infect many types of birds/mammals (it’s protein coat patters are like a master key) some have outer membranes

6. Viruses: Structure Bacteriophages = viruses that attack and infect specific bacterial cells Often used in biotechnology as tools to control particular bacterial diseases and in gene therapies

7. Viruses: How Do They Reproduce?? A virus must enter a host cell to reproduce Two Ways: 1)Lytic Cycle 2)Lysogenic Cycle Viruses are selective; they enter only specific cells of a specific host and are EXTREMELY small

8. Viruses: How Do They Reproduce?? 1)Lytic Cycle (destruction of host  release of more) Virus attaches to cell and injects its DNA/RNA Viral DNA takes over host cell to make new viral DNA and protein coat Viral components assembled Host cell lysis (explodes) releasing new viruses to infect more host cells May take as little as 25-45 minutes to complete

9. Viruses: How Do They Reproduce?? 2) Lysogenic Cycle (dormant) Virus does not kill host cell right away but rather viral DNA becomes incorporated into host DNA and remains dormant until lytic cycle triggered

10. Viruses: How Are They Positive?? Viruses are used in making vaccines against a virus or bacteria Viruses can be used in genetic engineering to transfer DNA into cells in a positive way

11. An Overview: Video #1: https://www.youtube.com/watch?v=Rpj0emEGShQhttps://www.youtube.com/watch?v=Rpj0emEGShQ Video #2: https://www.youtube.com/watch?v=s8jhJXgC-bkhttps://www.youtube.com/watch?v=s8jhJXgC-bk

12. Concluding Questions: 1)Is a virus considered a living thing? Justify your answer. 2)How is a virus able to enter a host cell? 3)Illustrate the lytic and lysogenic reproduction cycles of viruses.

13. To Do: Complete questions 1-8 on page 59 Have clear diagrams of Lytic cycle and Lysogenic cycle in notes