Chpt. 19:
Genetic Engineering
What is genetic engineering???
Genetic engineering: is the artificial manipulation
or alteration of genes.
Genetic Engineering involves:
• removing a gene (target gene) from one organism
• inserting target gene into DNA of another organism
• ‘cut and paste’ process.
Some important terms!!!
Recombinant DNA: the altered DNA is called
recombinant DNA ( recombines after small section of
DNA inserted into it).
Genetically Modified Organism (GMO): is the
organism with the altered DNA.
Genetic Engineering breaks the species
barrier!!!
• Genetic engineering allows DNA from different species
to be joined together.
• This often results in combinations of DNA that would
never be possible in nature!!! For this reason genetic
engineering is not a natural process.
• If DNA is transferred from one species to another the
organism that receives the DNA is said to be transgenic.
Genetic engineering breaks the species
barrier!!!
• Examples of cross-species transfer of genes:
- a human gene inserted into a bacterium
- a human gene inserted into another animal
- a bacterial gene placed in a plant
Alternative names for genetic engineering:
• Genetic Manipulation
• Genetic Modification
• Recombinant DNA Technology
• Gene Splicing
• Gene Cloning
Tools used in genetic engineering!!!
• Source of DNA: Target (foreign) DNA – DNA taken from
one organism to be placed into the DNA of a second
organism.
• A cloning vector: Special kind of DNA that can accept
foreign DNA and exactly reproduce itself and the foreign
DNA e.g. Bacterial plasmid (loop of DNA found in
bacteria).
Tools Used in Genetic Engineering
Restriction Enzymes:
- are special enzymes used to cut the DNA at specific
places.
- different enzymes cut DNA at specific base sequences
known as a recognition site. For example
i) One restriction enzyme will always cut DNA at
the base sequence: GAATTC.
ii) Another restriction enzyme only cuts at the
sequence: GATC.
- If DNA from two different organisms is cut with the
same restriction enzyme the cut ends from both sources
will be complementary and can easily stick together.
Restriction enzymes
DNA 1
DNA 2
Tools used in Genetic Engineering
DNA Ligase: enzyme which acts like a glue sticking
foreign DNA to DNA of the cloning vector.
• will only work if DNA from the two DNA sources has
been cut with the same restriction enzyme i.e. sticky ends
of cut DNA will be complementary to each other.
Please note diagram illustrating use of restriction
enzymes and DNA Ligase in production of recombinant
DNA Fig. 19.6 pg. 195
Process of Genetic Engineering
Five steps involved in this process:
1. Isolation
2. Cutting
3. Insertion (Ligation)
4. Transformation
5. Expression
Note: The following example will explain how a human
gene is inserted into a bacterium so that the
bacterium can produce human insulin.
Process of Genetic Engineering
1. Isolation:
• Removal of human DNA (containing target gene).
• Removal of plasmid (bacterial DNA) from
bacterium.
2. Cutting:
• Both human DNA and plasmid DNA are cut with
the same restriction enzyme.
• Normally plasmid has only one restriction site
while human DNA will have many restriction sites.
Please note diagram 19.7 pg. 196
Process of Genetic Engineering
Insertion:
• means that target gene is placed into the DNA of
the plasmid or cloning vector.
• cut plasmids are mixed with human DNA sections
allowing the cut ends to combine.
Transformation
Expression
Applications of Genetic Engineering
You must know three applications: one involving a plant,
one animal and one for a micro-organism.
Plants: Weed killer-resistant crops
• many types of crop plants have bacterial genes
added to them.
• these genes make the plants resistant to certain
weed killers (herbicides).
• this means that the weed killers kill the weeds but do
not affect the transgenic plants.
Applications of Genetic Engineering
Animals:
There is a growing trend to experiment with inserting
human genes into the DNA of other mammals. The
transgenic animals formed in this way will then produce a
human protein and secrete it into their milk or even into
their eggs.
Applications of Genetic Engineering
Animals: Sheep produce human clotting factor
• A human gene has been inserted into the DNA of
sheep.
• This allows the adult sheep to produce a clotting
chemical needed by haemophiliacs to clot their blood
– produced in the milk of the sheep.
Pharming: is the production of pharmaceuticals by
genetically modified animals i.e. sheep, cows, goats etc.
Pharming – using animals to make pharmaceuticals
Applications of Genetic Engineering
Micro-organisms: Bacteria make insulin
• The human insulin gene has been inserted into a
bacterium (E-coli).
• This allows the bacterium to produce insulin for use
by diabetics.
Ethical Issues in genetic engineering
The release of GMO’s into the environment:
• Danger of possibility of GMO’s being released into
the environment.
• GMO’s grown in bioreactors do not provoke as much
fear.
• GMO’s grown outdoors - fears of foreign genes they
contain being spread to other plants.
Ethical Issues in Genetic Engineering
GMO’s as a food source:
Outlined below are some fears associated with the use of
GMO’s as a food source:
• Cannibalism:
– eating an animal containing a human gene is a
form of cannibalism.
- feeding GMO’s containing human genes to animals
that would later be eaten by humans.
• Religious reasons: – eating pig genes that are inserted
into sheep would be offensive to Jews and Muslims.
• Offensive to vegetarians/vegans: – eating animal genes
contained in food plants cause concern.
Ethical Issues in Genetic Engineering
Animal Welfare:
• There is serious concern that animals will suffer as a
result of being genetically modified.
• use of growth hormones may cause limb deformation
and arthritis as animals grow.
Ethical Issues in Genetic Engineering
Genetic Engineering in Humans:
The following issues are a cause for concern:
• If tests are carried out for genetic diseases, who is
entitled to see the results?
• Tests on unborn babies – could this lead to abortion
if a disease is shown to be present?
• Insurance/lending companies – will they insist on
genetic tests before they will insure/lend money to a
person?
• Need for legal controls over the uses to which human
cells can be put.
• Development and expansion of eugenics.