1. Viruses Review

2. A virus is like a building contractor who has blueprints, but no building materials.
Explain this statement.

3. Are Viruses Living Things?
Are made of cells
Can reproduce
Contain genetic material
Grow and develop
Obtain and use materials and energy
Respond to the environment
Maintain homeostasis
As a group, change over time X X √ X X X X √
Are Viruses Living Things?

4. Viruses are not considered to be living because:
1. They use a host cell for energy
2. They use a host cell for replication

5. Viral Structure Viruses have a simple structure:
genetic material (DNA or RNA)
a protein coat called a capsid that surrounds the genetic material
Sometimes they have an envelope outside of the capsid (made of lipids and proteins).

6. Name tells you this virus infects bacteria

7. Name tells you this virus causes influenza

10. Viral size

11. Activity: Cell,Virus, or Both?
Contains nucleic acid as genetic material

12. Activity: Cell,Virus, or Both?
Can grow and develop

13. Activity: Cell,Virus, or Both?
Can only replicate in a host

14. Activity: Cell,Virus, or Both?
Can reproduce on its own

15. Activity: Cell,Virus, or Both?
Obtain and use materials and energy

16. Activity: Cell,Virus, or Both?
Respond to the environment

17. Activity: Cell,Virus, or Both?
Maintain homeostasis

18. Activity: Cell,Virus, or Both?
Can contain DNA

19. Activity: Cell,Virus, or Both?
Which is smallest?

20. Activity: Cell,Virus, or Both?

21. Activity: Cell,Virus, or Both?

22. Viruses vs. Cells Characteristics of Viruses only
Characteristics of Cells only
How viruses & cells are alike

23. How do viruses infect cells?
Once inside the host cell, one of two different processes can occur:
Lytic cycle
Lysogenic cycle

24. A. Lytic Cycle: Viral DNA enters a cell, reprograms the cell to makes copies of the virus, and causes the cell to burst releasing new viruses.

25. B. Lysogenic cycle: A virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell DNA. Lysogenic infections may become lytic if the viral DNA leaves the host DNA.

27. DNA Viruses vs. RNA Viruses
do not mutate frequently because they utilize the host cell's DNA polymerase to make more copies of the viral DNA.
DNA polymerase can proofread and correct errors (mutations) during DNA replication.
You only need a vaccine for a DNA virus once. Examples: smallpox, HPV (warts, cancers).

28. DNA Viruses vs. RNA Viruses
have a high mutation rate
when the cell copies RNA for new viruses, the enzyme used cannot proofread and fix mutations.
Examples: Influenza, common cold virus (rhinovirus).

29. DNA Viruses vs. RNA Viruses
Some RNA viruses use their RNA to make DNA - called retroviruses.
When retroviruses make a copy of the RNA as DNA, the DNA can integrate into host cell DNA causing a lysogenic infection. Example: Human Immunodeficiency Virus (HIV).