Very small Non-living particle Made up of nucleic acid and
proteins Can only reproduce by infecting living cells Do not carry
out respiration, grow or develop
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Viruses have an inner core of nucleic acid which contains
either RNA or DNA Has outer protein coat called a capsid.
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Envelope Lipid Membrane Envelope allows for extended survival
outside the cell in order to spread infection
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Viruses have different shapes and sizes. The arrangement of the
proteins in the capsid of a virus determines the viruss shape
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What characteristic do viruses share with all living organisms?
a. Respiration b. Metabolism c. Replication d. Movement
Slide 8
Fill in the blanks The nucleic acid core of a virus contains
________ or __________ All viruses contain a coat of ________ and a
core of _________
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: Influenza Smallpox Cowpox Ebola
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Chicken Pox virus, Human Papilloma Adenovirus (respiratory
infections, pink eye) HIV
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Tobacco Mosaic Virus
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Nucleic Acid: DNA or RNA Capsid
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The cell in which a virus replicates in Before a virus can
replicate it must enter a host cell Before it can enter a host cell
it must first recognize and attach to a receptor site on the plasma
membrane of the host cell.
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Attach Inject and/ or Incorporate genetic info Replicate
Assemble Lyse or Divide within host
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Most viruses are highly specific to the cells they infect. Ex:
Plant viruses only infect plants Bacteriophages are viruses that
infect bacteria Ex: bacteriophage T4 Viruses have two ways of
infecting the host cell: -Lytic Infection -Lysogenic Infection
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Viruses cause human diseases such as polio, measles, influenza,
and AIDS. Viruses attack and destroy certain cells in the body
causing symptoms of the disease The best way to prevent against
viral diseases is to prevent infection through vaccination.
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Viruses that contain RNA as their genetic material When
retroviruses infect a cell they produce a DNA copy of their RNA.
Called retroviruses because their genetic information is copied
backwards From RNA to DNA instead of DNA to RNA Retroviruses are
responsible for some types of cancer and HIV
Lytic Cycle virus injects its nucleic acid into the host takes
over the host cells metabolism causes host cell to start
replicating the viruses proteins and nucleic acids virus secretes
enzymes that lyse the host cells cell wall and releases new virus
particles these particles can attack other host cells Lytic
Infection causes host cell to be lysed and destroyed.
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Lysogenic cycle Lysogenic virus injects its nucleic acid into a
host cell Viral DNA is integrated into the host cells chromosome
called a prophage Every time host cell reproduces, the provirus is
replicated along with it every cell that originates from the
infected host cell has a copy of the provirus
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Retroviruses can cause some cancers Retroviruses that convert,
or transform, normal cells tumor viruses These viruses carry genes
that disrupt the normal controls over cell growth and division
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The lysogenic cycle can take place for many years At any time
the provirus can be activated and enter a lytic cycle host cell is
killed
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A lytic infection occurs when a a. Virus infects a bacterium
and kills it immediately b. Virus embeds its genome into the DNA of
the host cell c. Virus enters a cell, makes copies of itself, and
causes the cell to burst d. Virus inserts its DNA into the DNA of
the host cell and remains part of the host cell for many
generations
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A preparation of a weakened or killed virus or viral protein
When injected into the body, it stimulates the immune system in an
effort to create permanent immunity to the disease For vaccines to
be most effective it must be used before an infection begins.
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Vaccines are used for the prevention of viral infections
Vaccines are NOT used for bacterial infections
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DiseaseSymptomIncubation MeaslesRash, fever9-11 days
ShinglesPain, itching on skinYears WartsBumpy areas on skinMonths
Coryza (cold)Sneezing, runny nose, fever 2-4 days HIVFatigue,
weight loss2-5 years The symptoms and incubation time of a disease
can indicate how the virus acts inside its host cell. Which
diseases may be caused by lytic viruses? Which diseases may be
caused by lysogenic viruses?
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Was the first virus to be identified Causes disease in tobacco
plants
Slide 40
One group of viruses that contain RNA as their genetic
information are a. Oncogenetic viruses b. Retroviruses c. Capsids
d. Prophages