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Improved sanitation systems
Surgery with anesthesia
Vaccines and antibiotics
And the fourth will be Gene Therapy
• The selective delivery of genes into a patients
cells
create missing proteins
replace defective disease causing genes
Over 4,000 conditions are caused by damage to a
single gene, many others by several genes
Ex-vivo “outside the body”
adding blood cells with new DNA to the blood stream
but has a limited time span
Using bacteria like E.coli to produce billions of copies of a
human gene
Using viruses to carry the gene to specific cells in the body
A cutting enzyme called a Restriction enzyme
It cuts foreign DNA that enter bacteria, e.g. Eco. R1
A circular DNA molecule from a bacteria called a Plasmid
The E. coli bacteria has dozens of different plasmids
A section of the human DNA containing the gene you need
An enzyme to join the bacterial DNA and human DNA called ligase
Found in many bacteria
A defense mechanism which cuts foreign DNA
The DNA is not cut randomly, but at specific sequences called
Recognition sequences
The restriction enzyme Eco.R1 found in strain C, E. coli bacteria
They don’t make straight cuts, but produce sticky ends
These sticky ends can rejoin by forming hydrogen bonds and the
sugar-phosphates rejoining with the help of the enzyme ligase
The DNA produced by restriction enzymes cutting is called gDNA
We know of 200 different restriction enzymes
The Plasmid pSC101 was isolated from E. coli. It is useful for
gene therapy because it has only one sequence of GATTC in
its entire molecule
Plasmids can be used to replicate DNA segments of up to
4,000 base pairs in length
For longer length viruses must be used.
Using Bacterial Plasmid
Cut the Bacterial Plasmid using restriction enzyme called Eco R1
This produces a hole in the circular
Plasmid DNA
•Eco. R1 only cuts at the sequence
GAATTC
•This produces two identical ends
Plasmid
Also treat human DNA with Eco.R1 and you get
a section of DNA containing the gene you want
with two complementary ends as well!
Short sequence of DNA with sticky ends
approaches a Plasmid.
Human DNA
Bacterial DNA
Human DNA
The newly completed piece of DNA is called Recombinant DNA
Gene cloning can now be used to produce millions of copies
A Plasmid with human DNA
is put back into a E. coli
The bacteria expresses the DNA.
The bacteria then divides to produce
millions of copies bacteria and human
gene.
A Plasmid cut by a
restriction enzyme
Segment of DNA
approaches
Foreign DNA spliced
into Plasmid by
DNA ligase joins
phosphates and sugars
Plasmid enters
bacterial cell
Viruses can be used to transfer large pieces of human
DNA to a location in the Human body.
Viruses are made up of a molecule of nucleic acid and a
protein coat.
Their nucleic acid codes for protein coats, replication,
enzymes to break-in and out of particular cells.
You remove the part of the nucleic acid that does not code
for the above functions and add foreign DNA.
The virus can then be put into the blood stream and it will
enter the cell it is designed to attack and transfer its code
into that cell.
Some current uses & trials of gene therapy
•Introduction of genes for new blood vessels for clogged
arteries
•Introduction of genes into the blood stream that interferes
with the replication of HIV
•Human growth hormone for Dwarfism
•Insulin production
•Glowing mice
•Replacing the cytoplasm in eggs to produce healthier eggs
Injecting genes into the blood stream which are then carried to
the target cells by viral carriers where they unload their
genetic material.
This is then used by the body to produce proteins that fight the
disease.
For the next decade gene therapy will only be used on somatic
cells (only effect the patient and not their offspring)
You and bioethicists will have to decide the future!