Transcript 1 st step: Attachment

capsid
DNA
• 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
tail sheath
tail fiber
– Enveloped, helical, or
polyhedral
• 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
• 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
endocytosis
2nd Step: Entry
– Virus enzyme weakens cell membrane
– Genetic material (DNA or RNA) enters host cell
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?
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