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
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• 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
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• 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…
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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
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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
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2nd Step: Entry–Virus enzyme weakens cell membrane–Genetic material (DNA or RNA) enters host cell
endocytosis
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3rd Step: Replication–Virus DNA/RNA uses
ribosomes to make virus proteins–Virus proteins created
by transcription/ translation
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4th Step: Assembly–New virus proteins
are assembled in the cytoplasm
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5th Step: Release–Virus enzyme causes cell membrane to burst–Viruses are released to find new host–Cycle repeats
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1st step: Attachment = Same
2nd Step: Entry = Same
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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
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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
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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)
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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)
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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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