The Virus

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 Enveloped, helical, or polyhedral Virus Parts capsid DNA tail sheath tail fiber

Are viruses alive? No Yes Not made of cells or organelles Can’t reproduce on own Don’t metabolize energy Don’t perform cellular processes Reproduce Have nucleic acid Adapt to surroundings Have organization

Viral Replication Bacteriophages (infect bacteria) are often studied Replication is similar with many animal viruses Two ways: Lytic cycle & lysogenic cycle These two can intertwine, working together…

Viruses can enter cells different ways Endocytosis Fusing with cell membrane Bacteriophages pierce cells, injecting genetic material. colored SEM; magnifications: large photo 25,000; inset 38,000x

The Lytic Cycle 1st 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

The Lytic Cycle 2nd Step: Entry Virus enzyme weakens cell membrane endocytosis 2nd Step: Entry Virus enzyme weakens cell membrane Genetic material (DNA or RNA) enters host cell

The Lytic Cycle 3rd Step: Replication Virus DNA/RNA uses ribosomes to make virus proteins Virus proteins created by transcription/ translation

The Lytic Cycle 4th Step: Assembly New virus proteins are assembled in the cytoplasm

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

The Lysogenic Cycle 1st step: Attachment = Same 2nd Step: Entry = Same

Lysogenic Cycle 3rd 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

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

How is HIV contracted? High risk activities: Low 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 (used to be higher, but sanitation is better now)

What is AIDS? Acquired Immunodeficiency Syndrome AIDS results when: New Exposures to HIV (2006) Gender of those living with HIV (2003) Acquired Immunodeficiency Syndrome AIDS results when: 1) Less then 200 T cells per 1mm³ blood 2) Multiple symptoms/infections from HIV appear Therefore, the HIV virus causes the disease AIDS

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

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Panels travel around the world to help remember and raise awareness AIDS Quilt Panels travel around the world to help remember and raise awareness

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