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 HAPPY THURSDAY 
Bellwork:
What is a virus? How do viruses make
us sick? How are viral infections
treated? Can viral infections be
prevented? Write 37 words on the
topic.
Essential Question:
How do viruses spread
and cause disease?
Standard: describe the role of viruses in causing
diseases such as human immunodeficiency virus
(HIV) (B4C)
Our new unit:
Viruses
Virus and Microorganisms Notecards
Pre-AP Biology
Due Thursday (2/12/15)
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Antibiotic
Bacilli Shaped
Bacterium
Bacteriophage
Binary Fission
Cocci Shaped
Capsid
Conjugation
Gram Staining
Host
Human Immunodeficiency Virus
(HIV)
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Immunization
Influenza
Lysogenic Cycle
Lytic Cycle
Lyse
Microorganism
Parasite
Pathogen
Retrovirus
Spirilla Shaped
Vaccine
Virus
I. Viruses
A. All viruses have one thing in common:
1. They enter living cells and use the cell to
produce more viruses.
B. Virus Structure
-A virus is made of:
a) a core of DNA or RNA
b) A virus has either a capsid or an
envelope surrounding its genetic information.
-The capsid allows viral DNA or RNA to
enter a host cell.
Envelope
Capsid
Viral components
– Nucleic acids
• DNA or RNA
– Capsid
• Protein
– Envelope
• Lipid
– Spikes
• Used to attach to cell
• ONLY SOME VIRUSES
7
Generalized Structure of Viruses
virions having envelopes = enveloped viruses
virions lacking envelopes = naked viruses
Generalized Structure of Viruses
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10
Cellular Organisms vs Acellular Particles
Eukaryotic Cell
Viru
s
Prokaryoti
c Cell
Eukaryotic
Nucleus
1 ųm (1000 nm)
C. Virus Specificity
-Viruses are highly specific to the cells they infect
Examples:
1) plant viruses infect plant cells
2) animal viruses infect only certain related species of
animals
3) bacterial viruses infect only certain types of bacteria.
So, what about
zombies?
E. Retroviruses
1. Retroviruses are viruses that contain RNA as
their genetic information.
-Retroviruses get their name from the fact
that their genetic information is copied
backward, from RNA to DNA.
2. HIV is the most infamous retrovirus.
AZT is a medication
used to treat HIV by
stopping an enzyme
called reverse
transcriptase
Write this
on your
notes!
F. Viruses are parasites (use
other organisms to grow and
reproduce)
1. Viruses are NOT alive
because they do not:
a) grow and develop
b) obtain and use
energy
c) respond to the
environment
G. Vaccines
1. Viral diseases cannot be treated with antibiotics.
2. Vaccines are the best way to protect against viruses
a) A vaccine is a dead or weakened version of a virus
that is injected into a person to stimulate the
immune system.
b) Vaccines provide protection only if they are used
before an infection begins.
When a virus invades…
D. Most viruses are not harmful to humans.
1. A pathogen is a disease-causing agent.
2. Viruses cause disease by disrupting the body’s
normal equilibrium.
3. Viruses attack and destroy certain cells in the
body, causing the symptoms of the disease.
H. Viral Reproduction
1. Once viral genes are inside the host cell, two processes
may occur: the lytic cycle or the lysogenic cycle.
Lytic Cyle
a) Lytic Cycle
1. Viral genes are inserted into a
host cell and take control of the cell
2. After more viruses are made, the
host cell bursts and is destroyed
3. New viruses infect new host cells
b) Lysogenic Cycle
1. Virus makes its DNA a part of the host cell’s DNA
(integrates)
2. Virus’s genetic information (DNA or RNA) replicates with
the host cell’s DNA.
3. The DNA remains dormant in the host cell.
4. Virus’s DNA activates and switches back to the
lytic cycle.
DRAW
THIS!!!
- Since viruses can transport DNA and RNA into
cells, scientists are exploring Gene Therapy
- In Gene Therapy, viral genetic material is
replaced with new DNA
- In time, this could be used to cure genetic
diseases. Currently we have no cure for these
types of illnesses
c) Viral diseases result in cell death
Sage and Scribe: Cycle Steps
• Get into partners—decide who is
partner A and who is partner B.
–Partner A: Describe the steps for the
Lytic cycle.
–Partner B: Draw each step.
• After a few minutes, we will switch
to the Lysogenic Cycle and you will
switch roles.