Transcript Viruses

VIRUS Notes
Definition
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Viruses are tiny
particles unlike any
other organism. A
virus consists of
genetic material such
as RNA or DNA
wrapped in a protein
coat.
Characteristics of Life
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Homeostasis
Nutrition
Transport
Respiration
Synthesis
Growth
Excretion
Regulation
Reproduction
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Is a virus living?
Is it living?
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No, because a virus can not reproduce on
its own. It needs a host cells.
How does a virus’ size relate to the
size of the cell?
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Viruses are much smaller than a cell and
that is why they can easily get into a cell
How are viruses characterized?
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Characterized as:
Plant virus
 Animal virus
 Bacterial virus (bacteriophage)
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What are the two parts that
comprise a virus?
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Nucleic Acid Core
(either RNA or DNA)
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Protein Coat called a
capsid
Shapes of Viruses
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1. Rod shaped
(tobacco mosaic
virus)
Shapes of Virus
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2. Polyhedral
(Mumps)
Shapes of Virus
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3. Helical (Herpes)
How does a DNA virus replicate?
DNA virus produces RNA (transciption)
 RNA directs production of viral proteins
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OR
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Viral DNA combines with host cell’s DNA
(either plant or animal)
How does RNA virus replicate or
reproduce itself?
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Once inside the host, an RNA virus directs
the host cell to produce proteins
OR
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Viral RNA may make DNA
Retrovirus
Virus that has RNA as its genetic material
 Example is HIV
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Bacteriophage
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Virus that attacks a bacterial cell
Two types of infection:
A.
B.
Lytic Cycle
Lysogenic Cycle
Lytic Cycle
Bacteriophage attaches to host cell and
injects its DNA
 Foreign DNA produces more proteins in
the host cell
 Causes cell to lyse (or break open) and
the virus/phage is released into the host’s
body
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Lytic Cycle
Lysogenic Cycle
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Phage injects DNA into the host cell
Foreign/phage DNA integrates itself into a
chromosome
 Bacteria reproduces
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Lysogenic Cycle
Lytic vs.Lysogenic Cycle