VIRUSES

By: Kurt DawiecClass: 717Date: January 28th, 2010

What is a virus? A VIRUS: Can reproduce Is nonliving Does not have organelles Does not grow Does not take in food or make waste Is a piece of nucleic acid covered with

a protein (this protein is called a capsid)

What is a virus? A VIRUS: Needs the help of living things. A virus is a parasite. PARASITE - an organism that survives

by existing on or in a host organism

How big is a virus?

http://learn.genetics.utah.edu/content/begin/cells/scale/

How does a virus reproduce?

http://www.tvdsb.on.ca/westmin/science/sbi3a1/Bacvirus/Virusrep.htm

A bacteriophage virus:

Bacteriophage – virus that infects bacteria

How does a virus reproduce? 5 Steps: 1 – Virus attaches

to a cell

2 – Injects genetic material into the cell

How does a virus reproduce?

3 – Genetic material directs the cell to make more virus parts

• 4 – The parts form new viruses

How does a virus reproduce?

5 – The cell membrane bursts, releasing new viruses

How does a virus reproduce?

http://www.tvdsb.on.ca/westmin/science/sbi3a1/Bacvirus/Virusrep.htm

How does a virus reproduce?

A virus can be inside a living thing and remain inactive

Ex: cold sore

The cell is not always destroyed when viruses leave the cell.

Ex: HIV

How do we classify viruses?

Viruses are NOT in the five kingdom system

Scientists used to classify viruses based on the host (Ex: plant virus, animal virus)

Today viruses are classified by their shape and structure

How do we classify viruses?

3 characteristics used to classify viruses:

1 – Structure of capsid 2 – Type of nucleic acid (DNA or RNA?) 3 – The way the virus reproduces

Usually the common name of a virus is based on the disease that it causes

Example: Swine flu virus, Rabies virus

Head

Tail

Capsid

Tail Fibers