VIRUSES…IT’S LATIN FOR POISON

What is a virus?

small infectious agent that can replicate only inside the cells of other organisms. Viruses are too small to be seen directly with a light microscope.

What can all viruses do?

REPRODUCE!!! They can not reproduce on their own Viruses require a HOST cell to infect

and reproduceHOST= another organisms cell

What are viruses named after? Named after the disease they cause

Ex: Influenza virus causes the influenza or

the flu Poliomyelitis causes polio Chicken pox virus causes chicken pox

What is a virus that infects a bacterium called? Called a

bacteriophage

Viral Structure

2 Major Parts Inner Coregenetic info. Viruses have either RNA or DNA as genetic material Outer Core capsid head

Viral Replication Cycle

2 Types of Cycles LYSOGENIC and LYTIC Lytic Replication: virus injects genetic

info inside host cell, replicates, and lyses (burst and kills) the host cell as viruses leave the cell particle . ATTACH INJECT SYNTHESIZE LYSE

Lysogenic Replication: viral genetic info becomes incorporated with host cell. Viral genetic info is now replicated every time host cell makes new cell

LYTIC CYCLE

LYSOGENIC CYCLE

Viruses Website

http://leavingbio.net/VIRUSES%20WEBPAGE.htm

http://www.courses.fas.harvard.edu/~biotext/animations/lysogeny.html

http://www.courses.fas.harvard.edu/~biotext/animations/lyticcycle.html

PROVIRUS

Viruses that use the lysogenic cycle They incorporate themselves into the

host DNA Can replicate without lyses of the cell Retroviruses are proviruses HIV is an example a provirus

Why are retroviruses so different

Takes its genetic information (RNA) and tricks the host manufacture its viral DNA.

Host then replicates its own as well as the retrovirus DNA

Oncogenic viruses will convert normal cells into tumor cells (Oncoviruses, Lentiviruses)

First Virus Identified

Tobacco mosaic virus Infected tobacco and other plants Discovered in 1892 by Dmirti

Iwanowsk

Where do scientists suggest that viruses come from?

No clear answer Some suggest that they came from

parasites, others say that they were bits of genetic info that separated from a cell

Are all viruses bad?

No!!! Viruses are being used for gene

therapy. Take the bad genetic info out of the

virus and replace it with good genes and inject the virus into people that have defective genes.

Vaccinations- weaken or dead viruses are injected into you to promote immunity

Diseases that are caused by viruses?

Flu H1N1 Chicken Pox Measles HIV Rabies Small Pox Ebola LOTS MORE!!!!

The HIV Virus