Virus Notes Chapter 19 Section 19-2

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.

Ways viruses vary……. 1. Shape – they come in a variety of shapes. (see next slide) 2. Size 20-400 nanometers. 1 nanometer = 1 billionth of a meter. 3. Specificity = certain viruses only infect certain organisms…your dog can’t get chickenpox!  

Examples

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.

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 http://www.npr.org/templates/story/story.php?storyId=114075029

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.

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.

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

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