1. Take 5
A cell that is virally infected appears to be bursting and dying under the microscope. Which infectious cycle is the virus undergoing?
Sometimes viral DNA incorporates itself into the host's genetic material. What is the viral DAN called after this occurs?
Viruses are ______________.

2. Viral Replication Lab Download the app “iMotion HD”
Use this app to make an animation for the lysogenic cycle. You can do this with ONE partner or on your own.
Must include:
The whole cycle start to finish (each step)
Captions or a voice over explaining each step of the lysogenic cycle
You can use pictures, drawings, etc to make this project or edit it in iMovie (for the voice over)
Submit it through ebackpack by the end of class

3. Viruses
Ch 18.1

4. What is a virus? Example: flu (influenza)
It kills 0.5 million people every year worldwide (30,000 in the US)
A virus is 10X smaller than bacteria.
A virus is composed of nucleic acids that are enclosed in a protein coat.

5. Are viruses living?
NO!
They do not grow, develop, nor carry out respiration
Viruses can only replicate and they need a host cell to even do that.

6. How are viruses named? (part 1)
After disease they caused
rabies virus
The organ/tissue they infect
“adenovirus”  affects adenoid: tissue at back of throat/nasal cavity

7. How are viruses named? (part 2)
Given a genus name ending in “virus” and a species name
Virus that infects bacteria = “bacteriophage” or simply just “phage”
Some have code names: Type 1 – Type 7, depending on what it infects

8. What is the structure of a virus?

9. An inner core of nucleic acid (DNA or RNA: which are the instructions for copying)
Outer protein coat (aka “capsid”)

10. What is the structure of a virus?
Some have an extra envelope on outside
Many different shapes depending on what it infects

12. How do they attach to a host?
By locking the proteins on the outside to a host or grabbing on with its tail fibers

13. How do they attach to a host?
By locking the proteins on the outside to a host or grabbing on with its tail fibers

14. How do they attach to a host?
The attachment is a specific process!
Each virus can usually attach to only a few kinds of cells
Example: polio virus can only infect intestinal and nerve cells

15. The viruses are species specific
Ex: Smallpox virus infects only humans
Ex: West nile virus infects birds, horses, and humans

16. Viral Replication Cycle
Two cycles
Lytic cycle
Lysogenic cycle

17. Lytic Cycle

18. Lytic cycle Virus attaches to a host cell
Injects DNA/RNA into the host cell
Virus’ DNA is transcribed & translated
Substances produced take over host cell’s genetic material
Host cell provides enzymes and energy to make copies and assemble new viruses
Viruses burst from cell (killing it)

20. Lysogenic cycle Doesn’t kill cell immediately like in lytic cycle
Virus attaches and injects DNA/RNA
Virus DNA/RNA is integrated into cell’s chromosome
“Provirus”: viral DNA that is integrated into the host cell’s chromosome
Cell carries out activities
Every time cell replicates, provirus is replicated, too
At any time, virus can be activated and enter lytic cycle (not sure what causes it. Ideas: stress, sunburn, anxiety)
Ex: reoccurrence of cold sores

21. Lytic cycle vs. Lysogenic cycle

22. Disease symptoms of proviruses
lysogenic cycles
Disease symptoms of proviruses
Cold sores: herpes simplex I virus
Genital herpes: herpes simplex II virus
Hepatitis B virus
Chicken pox
Shingles

23. Retroviruses Ex: HIV: human immunodeficiency virus causes AIDS
Only has RNA
Complex replication cycle
Once inside host, a retrovirus makes DNA from its RNA using reverse transcriptase from inside its capsid
Retroviruses
It then integrates it into host cell’s chromosome (“provirus”)

24. HIV: An infection of white blood cells
HIV attacks white blood cells
Newly made viruses are released into blood stream to infect other white blood cells
Infected cells function normally because provirus only makes a few new viruses at a time (person may not appear sick)
You gradually lose white blood cells
& can’t protect yourself against disease

25. Cancer and Viruses Some viruses linked to cancers
Ex: hepatitis B may be causing liver cancer
These viruses disrupt normal growth and cell division, causing abnormal growth (tumors)

26. Plant viruses Over 400 viruses that infect plants & 1000 diseases
Viruses can stunt growth and cause yield crop loss
They require wounds or insect bites to enter host
Ex: Zucchini yellow mosaic virus

27. Plant viruses Viruses do not use surface recognition
Do not undergo lytic or lysogenic phases
Not all are fatal
Ex: Tobacco mosaic virus

28. Hospitals “full up”: 1918 Influenza Pandemic
Contagion Trailer:
How a virus changes the world:
Could “Contagion” Really Happen?