Biotechnology : 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
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 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.
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).
- Restriction Enzymes – are special enzymes used to cut the DNA at specific places. Different enzymes cut DNA at specific base sequences known as recognition site. For example: (1) one restriction enzyme will always cut DNA at the base sequence: GAATTC. (2) another restriction enzyme only cutes at the sequence: GATC.
- 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, ie, sticky ends of cut DNA will be complementary to each other.
Process of Genetic Engineering
- Isolation – removal of human DNA (containing target gene). Removal of plasmid (bacterial DNA) from bacterium.
- 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.
- Insertion – means the 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.\
Applications of Genetic Engineering
- 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.
- 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.
- 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 ie sheep, cows, goats
- 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 GMOs into the environment:
- Danger of possibility of GMOs being released into the environment.
- GMOs grown in bioreactors do not provoke as much fear.
- GMO’s grown outdoors – fears of foreign genes they contain being spread to other plants
- Animal Welfare
- There is a 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.
- Fears Associated with the use of GMOs as a food source:
- Cannibalism – eating an animal containing a human gene is a form of cannibalism. Feeding GMOs 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.