3. Virus: A biological particle composed of nucleic acid and protein Intracellular Parasites: organism that must “live” inside a host What is a Virus?

4. Reproduce Have nucleic acid Adapt to surroundings Have organization Not made of cells or organelles Can’t reproduce on own Don’t metabolize energy Don’t perform cellular processes

5. All Have: –1) Capsid: coat of protein that surrounds nucleic acid –2) Nucleic Acid: RNA or DNA Some Have: –Tail Fibers: Used for attachment (not legs) Shapes vary

6. Bacteriophages (infect bacteria) are often studied –Replication is similar with many animal viruses

7. 1 st Step: Attachment –Virus lands on cell membrane –Virus attaches to a cell receptor –No attachment = No infection –Virus acts as a “key” to the receptor

8. 2 nd Step: Entry –Virus enzyme weakens cell membrane –Genetic material (DNA or RNA) enters host cell endocytosis

9. 3 rd Step: Replication –Virus DNA/RNA uses ribosomes to make virus proteins –Virus proteins created by transcription/ translation

10. 4 th Step: Assembly –New virus proteins are assembled in the cytoplasm

11. 5 th Step: Release –Virus enzyme causes cell membrane to burst –Viruses are released to find new host –Cycle repeats

12. 1 st step: Attachment = Same 2 nd Step: Entry = Same

13. 3 rd step: Replication –Virus DNA combines with cell DNA, and waits Provirus = cell DNA + viral DNA –Cell divides by mitosis –Each new cell will contain the provirus

14. 4 th Step: Assembly Same, except many new viruses are being assembled in many cells 5 th Step: Release Same, except many cells burst releasing many more viruses

15. Retroviruses RNA viruses Contains the enzyme Reverse Transcriptase Steps –1) Virus RNA enters host cell –2) Cell’s ribosomes create virus DNA –3) Virus DNA combines with cell DNA (becomes dormant) –4) Cells divide as usual –5) Once active, normal steps of transcription/translation followed

16. How is HIV contracted? High risk activities: –1) Sex (oral, vaginal, anal) –2) Sharing needles (tattoos, piercings, drugs) Low risk activities: –3) Mother to child in womb –4) Breast milk –5) Blood transfusions

17. What is AIDS? Acquired Immunodeficiency Syndrome AIDS results when: –1) Less then 200 T cells per 1mm ³ blood –2) Multiple symptoms/infections from HIV appear Therefore, the HIV virus causes the disease AIDS Gender of those living with HIV (2003) New Exposures to HIV (2006)

18. Female Transmission of HIV (2006) Male Transmission of HIV (2006) Want more stats? Go to the Centers for Disease Control’s Website http://www.cdc.gov/hiv/topics/surveillance/united_states.htm