capsid DNA tail sheath tail fiber All Have: – 1) Capsid: coat of protein that surrounds nucleic acid – 2) Nucleic Acid: RNA or DNA Some Have: – Tail.

capsid

DNA

tail sheath

tail fiber

• 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

• 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

• 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

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

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

endocytosis

3rd Step: Replication–Virus DNA/RNA uses

ribosomes to make virus proteins–Virus proteins created

by transcription/ translation

4th Step: Assembly–New virus proteins

are assembled in the cytoplasm

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

1st step: Attachment = Same

2nd Step: Entry = Same

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

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:– 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:– 1) Less then 200 T cells per 1mm³ blood– 2) Multiple symptoms/infections from HIV appear

• Therefore, the HIV virus causes the disease AIDS

Gender of those livingwith HIV (2003)

New Exposures to HIV (2006)

Female Transmission of HIV(2006)

Male Transmission of HIV(2006)

Want more stats? Go to the Centers for Disease Control’s Websitehttp://www.cdc.gov/hiv/topics/surveillance/united_states.htm