To Figure Out What You Need on the Final… Score needed= (Goal - 0.8*Current Grade)/0.2 E.g. you have a 58. To pass the class Score needed = (59.5-0.8*58)/0.2.

To Figure Out What You Need on the Final…

Score needed= (Goal - 0.8*Current Grade)/0.2

E.g. you have a 58. To pass the class

Score needed = (59.5-0.8*58)/0.2 = 65.5

VirusesRunaway Genetic Material

What is a virus?Genetic material (DNA or RNA, single or double stranded)

A protein coat

Sometimes a few more proteins

Sometimes a membrane

Notice viruses have…

No organelles of any kindNo ribosomesCan’t really make or do anything on their own

Why aren’t viruses considered living?No homeostasisNo growthNo real metabolismNo real response to environmentNot organized into cellsReproduction is dependent on host

They do adapt/evolve

What do Viruses Do? Insert genome into a host Replicate using host machinery (DNA polymerase,

RNA polymerase, ribosomes) Reassemble and infect new hosts

DNA Viruses RNA viruses

Types of Viruses

May insert into host or just copy and leave

E.g. chickenpox, smallpox, herpes, hepatitis B

Makes copies and leaves cell

E.g. cold, flu, rabies, ebola

Retro viruses

Use reverse transcriptase to make DNA from RNA

Insert themselves into the genome

E.g. HIV

RetrovirusesRetroviruses like HIV insert DNA into our genome

Once there it’s near impossible to removeCan transcribe to make new viruses and proteins that are necessary to assemble new viruses

Where Did Viruses Come From?

Viruses are extremely diverse, so it seems unlikely that all viruses are related

3 main hypotheses, all of which could be correct

1. Viruses “escaped” from hostViruses tend to be genetically similar to hostsGenes move and copy themselves in similar ways to many viruses

2. Viruses were living things that lost most of their machinery

Many parasitic bacteria like Chlamydia are thought to have evolved from free-living ancestors

Over time parasites lose genes and become much smaller and simpler

3. Viruses were here firstViruses are the most primitive organisms and have co-evolved with new forms of life

Why is it Hard to Treat Viruses?There’s nothing to attack!Antibiotics attack the cell wall of bacteria or their ribosomes. Viruses have neither

They mutate often due to lack of proofreading (especially retroviruses)

Once they are part of the genome there’s no real way to attack them

VaccinesPiece of a virus (e.g. one protein) or inactivated virus

Stimulates immune system to create antibodies ahead of time

Prevents virus from invading cells in the first place

Self-Destruction Your immune system recognizes infected cells and destroys

them

Viruses are NecessaryKeep bacteria in checkEstimated to kill 20% of the biomass of the ocean each day

Recycles nutrients and provides new opportunities for other organisms

ReviewFor the test you should know:

1.the basic structure of a virus

2.why viruses are not considered living

3.how a retrovirus operates

4.the 3 potential origins for viruses

5.how our body deals with viruses

You DO NOT need to know

1.Specific viruses other than HIV

2.The specifics of how T cells operate

3.Specifics on how DNA or RNA viruses operate (just know they copy themselves, make proteins and reassemble

4.The fun facts

Fun Facts About VirusesAbout 8%-50% of the human genome is thought to have originated from infectious viruses

About 1030 viruses on Earth. Lined up end to end they would stretch 200 million light years out! (longer than the entire length of our galaxy)

1016 copies of HIV are generated each dayA liter of seawater contains 100 billion virusesHIV has only about 10 genes. The smallest virus ever discovered has only 2 genes

http://www.virology.ws/2009/10/19/ten-cool-facts-about-viruses/

http://discovermagazine.com/2010/apr/20-things-you-didnt-know-about-viruses