Text of Chpt. 19: Genetic Engineering. What is genetic engineering??? Genetic engineering: is the artificial...
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 GMOs into the environment: Danger of possibility of GMOs being released into the environment. GMOs grown in bioreactors do not provoke as much fear. GMOs grown outdoors - fears of foreign genes they contain being spread to other plants.
Ethical Issues in Genetic Engineering GMOs as a food source: Outlined below are some 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.
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.