1. Unit 11 – Viruses, Bacteria, and Protist

2. electron micrograph of a cluster of influenza viruses
What is a Virus?
A virus is a tiny particle made of protein and genetic information
electron micrograph of a cluster of influenza viruses

3. What is a Virus? A virus has 2 parts… genetic material –
a) the genetic information in viruses may be either RNA or DNA.
b) viruses contain a very small amount of genetic material

4. Genetic Material DNA/RNA
What is a Virus?
Capsid
the Capsid is a shield made of protein that protects the genetic material.
LABEL THIS VIRUS:
Capsid
Genetic Material DNA/RNA

5. What Do Viruses Do?
Viruses inject other cells with their genetic material in order to replicate.
Each type of virus infects a particular kind of cell in a specific organism.
The specific organism that a virus attacks is called its host.

6. How Do Viruses Replicate?

7. How Do Viruses Replicate?
Steps of Viral Replication
The virus attaches to a host cell
The virus injects its information into the host cell

8. How Do Viruses Replicate?
The genetic information of the virus takes control of the host cell and orders the production of new viruses.
New viruses are assembled in the host cell

9. How Do Viruses Replicate?
So many viruses are made inside the host cell that the cell bursts.
The new viruses leave the host cell and go on to infect new cells.

10. Two Ways of Replicating
It can go through the Lytic Cycle.
The virus inserts its DNA in to the hosts DNA, takes control of it and orders it to create virus DNA and new viruses.
If it goes through this cycle it destroys the host cell when it lyses (bursts) the cell.

12. Two Ways of Replicating
It can go through the Lysogenic Cycle.
The virus also inserts its DNA into the host’s DNA… but instead of it taking over, it remains in the DNA and replicates as part of the host’s DNA when the cell goes through mitosis.
No new viruses are created.
If it goes through this cycle the host cell is conserved
(not destroyed).

14. Viral Diseases and Treatment
Examples of Viral Diseases
Influenza (Flu)
HIV (AIDS)
Herpes
Chicken Pox
Treatment
A virus causes a disease when it destroys its host cells during the lytic cycle.
A virus can not be treated once you have been infected. Antibiotics have NO effect on it.
Viruses can only be PREVENTED by Vaccines.

15. Quick Check #1

16. Quick Check #2

17. Quick Check #3
Compared to lytic viruses, lysogenic viruses DO NOT . . .

18. Quick Check #4

19. Quick Check #5
In the table below, which organism (I, II, or III) is a virus?