DENT LECTURE 11 Biotechnology Genetic Engineering.pdf

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A practical use of our understanding of heredity….
Genetic Engineering - changing the phenotype by changing its DNA to make it more useful/desirable.
Used to domesticate animals and plants
Only technology required is the ability to select and breed the next generation
Can wait for useful mutations to arise by chance… and/or cross two related species.
Must wait a long time for the right gene to mutate into a new form
i.
ii.
limitations:
Ex. Cabbage + Radish = Cadish? (result leafy part of radish and roots of cabbage...T.T)
Selective breeding technology (i.e. domestication of plants and animals)
To make an organism express a new phenotype
1)
To understand how the gene itself works (in isolation)
2)
Why clone?
Gene cloning - taking a single gene form one organism and putting it in another organism.
Example: Diabetes and Insulin -cloning a gene to make bacteria produce a useful protein.
Your body regulates the amount of glucose using only a relatively small number of cells called beta islet cells in your
pancreas.
They sense the amount of glucose and release the hormone insulin which signals to the rest of the body that glucose is
served - liver cells should start absorbing glucose from the blood stream. When low on glucose: the hormone, glucagon is
released to tell the liver to release glucose into the blood for other cells to eat.
In diabetes, the islet cells are destroyed by an autoimmune reaction, thus your body no longer has any way to know when
glucose is served. Even if glucose is there, your cells ignore it. But the body has to get rid of unused glucose… You starve,
bathed in glucose.
FredericK Banting and Charles Best : purified insulin from dogs to show
that it could be used to treat diabetes by substituting the insulin that
the diabetics were not making for themselves.
Where do you get the insulin?? --> Purified from pig pancreases since
pigs are very similar to humans and they are expendable. --> Problem:
1)very expensive, 2) pig insulin is not exactly like human insulin; people
So… maybe not pigs..
often form immune reactions to it.
About diabetes…….
In late 1970s… "Hey, we can take the human gene for insulin and put it into some cells that can grow tons of thus making tons of
human insulin to treat diabetics!"
Where to get the human gene
1)
How to put it into another organism so that it would be inherited
2)
How to get it expressed
3)
Three obstacles:
E. coli, yeast, cultured vertebrate cells - that make
human insulin in large quantities.
We can grow very easily:
Solution:
Make a gene, put it in a plasmid and transform it into
bacteria!
Problem#1:
Bacteria don't know how to splice , so the insulin gene
cannot have introns. A gene without introns? Make a DNA
copy of the mRNA from which the introns have already been
spliced out. How to make a DNA copy of an mRNA? Use the
reverse transcriptase enzyme from a retrovirus. This DNA
copy of the mRNA --> cDNA (copy of RNA)
Problem#2:
How to find the insulin mRNA in the midst of other
thousands of mRNAs in a cell? You don't. You make ALL of
the mRNAs into cDNAs and then clone each cDNA into a
Plan
DENT LECTURE 11: Biotechnology: Genetic Engineering
BIOL Page 1
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