Transcript Virus - Cloudfront.net

What is a Virus?
• Virus: A biological particle composed of nucleic
acid and protein
• Intracellular Parasites: organism that must “live”
inside a host
• Not made of cells
• Can’t reproduce on
own
• Don’t metabolize
energy
• Don’t perform cellular
processes
• Reproduce with
help of host
• Contain nucleic
acid
• Adapt to
surroundings
• Have
organization
• 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
Virus Video
• Bacteriophages
(viruses that
attack bacteria)
are often studied
• Replication is
similar with many
animal viruses
• Two “life” cycles:
Lytic & Lysogenic
Dozens of phage viruses attacking an
E. coli
bacteria
The
bacteria
cellcell
is destroyed
and new viruses escape
1st Step: Attachment
– Virus lands on cell
membrane
– Virus attaches to a
cell receptor
– Virus acts as key;
receptor acts as lock
2nd Step: Entry
– Virus enzyme
weakens cell
membrane
– DNA/RNA enters the
host cell
Another way viruses may enter a
cell… through phagocytosis
3rd Step: Replication
– Virus DNA/RNA
uses ribosomes to
make virus proteins
– Virus proteins
created by
transcription/
translation
Viral DNA
transcription
Viral RNA
translation
Viral Proteins
4th Step: Assembly
– Virus proteins are
assembled into
new viruses
5th Step: Release
– Virus enzyme
causes cell
membrane to lyse
(burst)
– Viruses are
released
– Cycle repeats
Attachment
All stages on
one slide
Entry
Replication
& Assembly
Release
1st step: Attachment
Same
2nd Step: Entry
Same
3rd step: Replication
– Provirus Created
Virus
DNA
• Virus DNA
combines with cell
DNA
– Infected cell
divides by mitosis
and copies the
provirus
– Each new cell will
contain the
provirus
Provirus
Procell
virus
DNA
Provirus
4th Step: Assembly:
new viruses are
assembled in many
cells
5th Step: Release
many cells burst
releasing many
more viruses
The viral DNA become active and starts making new viral proteins
The infected cells burst…releasing the new viruses
Retroviruses
• Type of RNA virus
• Contain enzyme called
“reverse transcriptase”
• Steps
– 1) Virus RNA enters host
cell
– 2) Reverse transcription
changes the virus RNA
into DNA
– 3) Virus DNA combines
with cell DNA (provirus
created)
– 4) Cell divides and copies
the virus
– 5) Eventually, the viral
DNA becomes active
How is HIV contracted?
High Risk Activities
Low Risk Activities
• High risk activities: • Low risk activities:
– 1) Sex (oral, vaginal,
anal)
– 2) Sharing needles
(tattoos, piercings, drugs)
– 3) Mother to child in womb
– 4) Breast milk
– 5) Blood transfusions
HIV Prevention
• 100% Effective:
Abstinence (not
participating in sexual
acts)
• If sexually active:
Latex condoms are the
only forms of birth
control that prevent
STDs and pregnancy
• If drug user: Change
needles
What is AIDS?
New Exposures to HIV (2006)
Gender of those living with HIV (2003)
• Acquired Immunodeficiency
Syndrome
• AIDS results when:
– 1) Amount of T-cells drop
(200 T-cells per 1mm³
blood)
– 2) Multiple
symptoms/infections
appear
• Rash, fever, headache,
sore throat, swollen
lymph nodes
• Therefore, the HIV virus
causes the disease AIDS by
killing your T-cells
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
1.
2.
3.
4.
5.
6.
7.
8.
True or False: All viruses have a capsid, nucleic acid, and tail fibers.
List 3 reasons why viruses may be living? Nonliving?
What is the virus capsid made from?
What type of organism do phages infect?
In order list the stages of the lytic/lysogenic cycles.
In which stage…
• does the host cell explode?
• are virus proteins built to make new viruses?
• is a provirus created?
• does a virus connect with the host cell’s receptors?
Name the enzyme found within retroviruses.
The picture shows the normal stages of protein synthesis. Fill in the question marks
with the words: Translation, Protein, Transcription, DNA