Genetic engineering and cloning

Genetic engineering

The transfer of a gene or section of DNA from one organism into the DNA of another organism

Recombinant DNA

DNA of two different organisms combined as a result of gene transfer

Transgenic organism

When an organism contains DNA from a different species

Restriction enzymes

Enzymes that cut DNA molecules at specific points.

DNA ligases

Enzymes that join two DNA strands together.

Vector

Something used to transfer DNA into a cell

2 main vectors

• Plasmids- Transfer DNA into bacteria or yeast

• Some Viruses- Transfer human DNA into human cells or bacteria

Process of manufacturing human insulin

• The gene is located inside a human chromosome

• The gene is then cut using restrictions enzymes, leaving it with “sticky ends”

• A bacterial plasmid is cut with the same restriction enzyme, leaving it with corresponding “sticky ends”

• The plasmid and the gene are then joined using the DNA ligase enzyme- this will form a single, unbroken molecule of DNA

• The recombinant plasmid is inserted into a bacterial cell

• When the bacteria reproduces, the plasmid will reproduce as well, all new bacteria will express the human insulin gene and make the human insulin protein.

• This genetically engineered bacteria can be placed in a fermenter to reproduce rapidly so that large quantities of the human protein can be created.

Why is bacteria useful for genetic engineering

• No ethical concerns over manipulation and growth

• Presence of plasmid makes them easy to remove and manipulate.

• Same genetic code as organisms that genes are taken from, making it easily readable and produce the same proteins.

Reasons to genetically engineer crops

• Higher yield

• Higher nutritional value

• Resistance to disease and pests

Advantages of GM plants

• Environmentally friendly as pesticides and herbicides (chemicals) are not being used.

• Cheaper + less time consuming for farmers

• Higher crop yield due to less competition with weeds

Disadvantages of GM plants

• Higher cost as GM seeds are more expensive to cover the cost of developing them.

• Reduces biodiversity

• Risk of inserted genes being transferred to wild plants by pollination

What is a simple method to clone plants

• Cuttings- Cut a stalk at a slant from the parent plant, dip it in rooting powder, and plant it to create an identical plant to the parent.

Micropropagation process

• Cells are scraped from the parent plant (explants)

• The surface of these explants is sterilised using a disinfectant followed by a rinse with sterile water

• Sterilised explants are placed in a sterile petri dish containing sterile nutrient agar

• The growth medium encourages the explant cells to grow and divide into small masses of cells (a callus)

• Each callus is transferred to a fresh growth medium which contains plant growth regulators (hormones)

• These hormones causes the callus to develop a stem, roots, and leaves, forming a plantlet.

• Plantlets can be transferred into individual potting trays to develop into plants.

Advantages of micropropagation

• Cheaper

• Greater yield in a short amount of time

• Identical

• Immune to certain diseases

Disadvantages of micropropagation

• Trained personnel and sterile equipment are required

• Genetically identical- vulnerable to the same disease and pests

Embryo cloning process

• Egg cell from an ideal female mammal is artificially fertilised using sperm cell from ideal male mammal- forming an embryo

• The developing embryo is then split apart many times before the embryo becomes specialised- forming many separate embryos that are genetically identical

• These cloned embryos are then transplanted into host mothers and all offspring are genetically identical

Adult cell cloning process

• Nucleus is removed from an unfertilised egg cell

• Nucleus from an adult cell (eg. skin cell) is inserted into the egg cell

• A small electric shock stimulates the egg cell to divide (by mitosis) and forms an embryo

• The embryo is then inserted into an adult female (surrogate mother) and then develops until birth

Advantages of cloning

• Preservation of endangered species

• Increases yield

• A fast method of producing high quantities at any time of year.

Disadvantages of cloning

• Lack of diversity- vulnerable to the same diseases and pests

• Cloned animals are not as healthy as normal animals

• Ethical concerns

Pharming process

• A transgenic animal is bred that contains a foreign gene within its genome- this causes the animal to produce a useful compound that will be expressed within its milk

• Once this has been done the animal can be cloned to produce a whole herd or flock, all of which produce the same special milk

What can pharming be used to produce

• Antibodies for targeting cancer cells in humans

• Blood clotting factor IX for haemophilia (blood clotting disorder)

• Alpha-1-antitrypsin for cystic fibrosis sufferers