1. 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 = ( *58)/0.2 = 65.5

2. Runaway Genetic Material
Viruses
Runaway Genetic Material

3. What is a virus?
Genetic material (DNA or RNA, single or double stranded)
A protein coat
Sometimes a few more proteins
Sometimes a membrane

4. Notice viruses have… No organelles of any kind No ribosomes
Can’t really make or do anything on their own

5. Why aren’t viruses considered living?
No homeostasis
No growth
No real metabolism
No real response to environment
Not organized into cells
Reproduction is dependent on host
They do adapt/evolve

6. What do Viruses Do? Insert genome into a host
Replicate using host machinery (DNA polymerase, RNA polymerase, ribosomes)
Reassemble and infect new hosts

7. Types of Viruses DNA Viruses RNA viruses Retro viruses
Makes copies and leaves cell
E.g. cold, flu, rabies, ebola
Use reverse transcriptase to make DNA from RNA
Insert themselves into the genome
E.g. HIV
May insert into host or just copy and leave
E.g. chickenpox, smallpox, herpes, hepatitis B

8. Retroviruses Retroviruses like HIV insert DNA into our genome
Once there it’s near impossible to remove
Can transcribe to make new viruses and proteins that are necessary to assemble new viruses

9. 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

10. 1. Viruses “escaped” from host
Viruses tend to be genetically similar to hosts
Genes move and copy themselves in similar ways to many viruses

11. 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

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

13. 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

14. Vaccines Piece 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

15. Self-Destruction
Your immune system recognizes infected cells and destroys them

16. Viruses are Necessary Keep bacteria in check
Estimated to kill 20% of the biomass of the ocean each day
Recycles nutrients and provides new opportunities for other organisms

17. Review For the test you should know: the basic structure of a virus
why viruses are not considered living
how a retrovirus operates
the 3 potential origins for viruses
how our body deals with viruses
You DO NOT need to know
Specific viruses other than HIV
The specifics of how T cells operate
Specifics on how DNA or RNA viruses operate (just know they copy themselves, make proteins and reassemble
The fun facts

18. Fun Facts About Viruses
About 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 day
A liter of seawater contains 100 billion viruses
HIV has only about 10 genes. The smallest virus ever discovered has only 2 genes