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MCDB 1041 Class 28
Learning Goals:
• Compare the creation of a multi-cellular transgenic
animal with a transgenic bacterium
• Explain the importance of the promoter region in
the production of transgenic animals
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A piece of DNA that is combined
with another piece of DNA not
usually associated with it is
Recombinant DNA
An organism that contains DNA from
another organism in its genome is
called a Transgenic organism
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A transgenic animal has a modified piece of DNA
(from another organism, or altered in some way)
present in:
a. every cell.
b. a particular set of cells, determined by the
scientist
c. a few random cells of the animal
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To grow a whole animal that contains the foreign
piece of DNA:
•  Recombinant DNA is injected into a
fertilized embryo in a culture dish, before it
starts dividing
•  As a result, all of the cells of the organism
will have the genetic alteration present
(whether it’s a plant or an animal). A
bacterium, since it is a single cell, obviously
just contains the altered piece of DNA.
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The foreign gene becomes incorporated into one of
the chromosomes in the host embryo.
(this is a rare and random event)
If the transfer occurs, then as embryo grows, all
cells within embryo will now have this gene
incorporated into a chromosome
-Bacterium directly infects a cell (works with plants)
-inject recombinant DNA into a fertilized embryo
Fig. 14.3b
-Use a virus to infect the cell
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Genetically Modified Foods
• 
• 
• 
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higher yield
improved quality
pest or disease resistance
tolerance to heat, cold and drought.
Plants have been bred for years to
specifically yield these desirable
qualities
Transgenic technology allows the
introduction of genes from OTHER
organisms into a plant or animal to
yield a specific outcome
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Insect Resistance
Bt corn
Normal corn
Bacillus thuringiensis
(Bt) (a bacterium):
Makes a protein that
causes paralysis and
death to some
insects (corn weevil).
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Use this rather than an applied
pesticide, which often kills beneficial
insects as well!
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Key difference between transgenic bacterium and
a transgenic animal (multicellular):
You don’t want to spend the time making the
transgenic animal only to kill it to isolate the
protein for humans!
Thus, the animal has to be engineered so that it
produces the human protein only in a particular
tissue (for example, the cells that produce milk)
Then the protein can be harvested.
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What controls “expression” of a gene (creation of
RNA from the DNA and ultimately production of
protein) in a transgenic animal?
a. The sequence of the gene itself
b. The transcriptional start site
c. A promoter region just before the beginning of the
gene
d. The transcriptional stop sequence at the end of
the gene
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Modifying the expression of a gene
To ensure that a recombinant piece of DNA is expressed
(translated into protein product) at the right place and time, a
specific promoter sequence is added upstream of the coding region
This promoter sequence is from a gene which is normally expressed
in the tissue of interest.
Gene of
interest
Extract DNA
Isolate
the gene
Add promoter to tell gene
where to be expressed
promoter
Promoter only activated in certain cells
So human protein only produced in certain cells
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Transgenic animals can make human protein
•  casein is a gene
produced in milk
•  the casein promoter is
bound by transcription
factors present only in
milk producing cells
•  since this is hooked to
the human gene, the
human gene will be
bound by TFs only in
those cells
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Used for treating Pompe disease, heart failure due to accumulation
of glycogen
A recombinant piece of DNA is made
The DNA is injected into an oocyte, then
fertilized
The rabbit is born and grows up
The rabbit produces protein, and that protein
can be harvested and given to humans
Other examples
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Disease model: Transgenic pigs
that have the human
Alzheimer's disease-causing
allele.
Used to study the disease and
potential treatments
Human drugs: Transgenic
goat that produces
recombinant human antithrombin III (rhAT) in their
milk. This protein prevents
blood from clotting.
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Try this application question:
You visit a sheep farm where they engineer sheep to produce human
growth hormone. They test the sheep when they are young to
determine if they are transgenic.
Human growth hormone is 10 KB. Sheep growth hormone is 5 KB. A
single set of PCR primers amplify both of these genes from a tissue
sample from the sheep.
Which of the following lanes correctly represents the DNA from a
sheep that is transgenic for human growth hormone?
Top of gel (-)
A.
10
5
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B.
C.
D.
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Handout!
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