capsid dna tail sheath tail fiber all have: – 1) capsid: coat of protein that surrounds nucleic...
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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
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