Download LEQ: How does RNA help to make a protein?

Lytic – viral
replication cycle
resulting in the
release of new
viruses by breaking
open the host cell.
Viral DNA directs host
cell to make new
viruses.
Lysogenic – viral
replication cycle in
which the viral
genome is
incorporated into the
host chromosome as
a prophage – new
phages are not
produced and host is
not destroyed
1. Envelope of virus
fuses with cell
membrane
2. Enzymes remove
protein coat
3. Viral enzyme uses
the viral RNA genome
as a template for
making
complementary RNA
which can do 2 things
4. produce viral protein
5. produce more viral
RNA
6. New protein coats
surround new RNA
7. Virus leaves the cell
by coating themselves
with cell membrane
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Enveloped DNA virus
that reproduces in
the host cell nucleus
Can remain dormant
in certain nerve cells
for long periods of
time
Stress activates
herpes virus flare ups

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This virus attacks nerve
cells which do not
divide  damage is
permanent
Treated with vaccine
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Stunt plant growth & diminish
crop yields
Common plant virus –
tobacco mosaic
Viruses enter through
damaged tissue
Viruses transmitted to plants
via…
› insects, gardeners and
farmers using contaminated
tools, infected plant to
offspring

How would a virus spread
through an individual plant?
› plasmodesmatta
AIDS – Acquired
Immune
Deficiency
Syndrome
Caused by HIV –
a RETROVIRUS
(uses reverse
transcriptase)
early 80’s 1st cases
in US in San
Francisco
Infects and kills several
kinds of white blood cells
RNA virus that
reproduces by means of
a DNA molecule; it
reverse transcribes its
RNA into DNA; its DNA is
inserted into the
chromosome; its DNA
then transcribes the
production of more viral
RNA and viral protein
 AIDS is a retrovirus
because it has…

› 2 copies of RNA
› Reverse Transcriptase
Acquired Immune
Deficiency Syndrome
and Human
Immunodeficiency Virus
- are named for what
they do - wipe out the
immune system.
1. Viral envelope fuses with
cell membrane
2. Enzymes remove protein
coat
3. Reverse transcriptase
converts viral RNA into
DNA
4. DNA is integrated into host DNA
5. Viral genes are transcribed to produce more viral RNA
and protein
6. New viruses are assembled
7. New viruses exit the cell taking host cell membrane
with them
*Retroviruses can be dormant for years before being expressed
Ebola
Recognized in
1976 in Central
Africa
Causes
hemorrhagic
fever, vomiting,
massive
bleeding and
circulatory
failure – often
fatal
West Nile
First seen 1990 in
North America
Causes
encephalitis
(swelling of the
brain)
Spread by
mosquitoes
SARS – Severe
Acute
Respiratory
Syndrome
February 2002 in
China
Within 3 months
8,450 were
infected – 10%
died
Caused by
corona virus
H1N1 / Swine Flu
2009 outbreak in
Veracruz,
Mexico
Typical flu
symptoms
Virus killed more
than 18,000
Mutations of existing viruses can produce
new viral diseases; diseases evolve into a
new species that can infect individuals who
were immune to the original strain
 People come in contact with other species
in the process we are exposed to the viruses
that infect the other species
 Spread of viral diseases is rapid due to
globalization (worldwide travel),
promiscuity, blood transfusions, intravenous
drugs, etc…
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Transformation – the incorporation of new
genes into a cell from DNA that cell takes up
from the surrounding environment (Griffith)

Transduction – the transfer of bacterial
genes from one bacterial cell to another by
a phage

Conjugation – the union (“mating”) of 2
bacterial cells resulting in the transfer of DNA
between the 2 cells
New DNA integration occurs by crossing over between the 2 DNA
molecules – incorporating new DNA into existing DNA
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Plasmid – small circular DNA found in bacteria
(and yeast) that is separate fro the
chromosome
F Factor – a piece of DNA that can exist as a
plasmid; it carries the genes needed to make
sex pili & other structures needed for
conjugation; F = Fertility; allow for the spread
of DNA to other cells

R Plasmid – bacterial plasmid that carries
genes for enzymes that destroy particular
antibiotics – result in antibiotic resistant
bacteria.