1. Virus Notes
Chapter 19
Section 19-2

2. Virus Characteristics
Viruses are particles of nucleic acid, protein, and lipids that invade living cells and reproduce. They are composed of a core of DNA or RNA surrounded by a protein coat called a capsid.
Examples of Viruses: Influenza, colds, chicken pox, measles, polio, and AIDS.

3. Ways viruses vary…….
1. Shape – they come in a variety of shapes. (see next slide)
2. Size nanometers.
1 nanometer = 1 billionth of a meter.
3. Specificity = certain viruses only infect certain organisms…your dog can’t get chickenpox!

4. Examples

5. Retroviruses
Retroviruses: Contain RNA as their genetic information. It is then copied to DNA. This is “backwards” or “retro”.
Viruses are considered parasites because they must infect a living cell in order to grow and reproduce.

6. Viral Reproduction #1
1. Lytic Infection – a virus enters a cell, makes copies of itself and causes the cell to burst
Attaches, entry, replication, assembly and release

7. Viral Reproduction #2
Lysogenic Infection – a virus integrates its DNA into the DNA of the host cell. It many remain inactive for a period of time.
The viral DNA is called a prophage.

8. 3 Ways to control viruses:
1. Vaccine – a weakened dose of the virus. When injected it usually prompts the body to produce an immune reaction to prevent illness.

9. Ways to control viruses:
2. Interferon – proteins that prevent virus from attaching to your cells and reproducing.

10. Ways to control viruses:
3. Antibodies – immune system proteins that attack and kill bacteria and viruses.