Genetic Modification 5.12-16

Genetic modification is the removal of a gene from one organism and inserting it into the DNA of another organism often of a different species. This is sometimes called recombinant DNA technology, this DNA is called the transgenic organism or GMO (genetically modified organism)

Restriction Enzymes 5.12-14

these enzymes are used to cut DNA molecules at specific points (recognition sites). Recognition sites are a short sequence of bases specific to the restriction enzyme. These enzymes often cut the DNA at a staggered cut (sticky end) leaving single strands of exposed bases. If they’re a straight cut they’re called blunt ends.

The same restriction enzyme is used to cut out the useful gene and the vector into which the useful gene will be inserted. So the sticky ends of the gene are complementary to the sticky ends of the vector. Ligase enzymes are then used to catalyse the joining of the ends together.

Vectors are normally plasmids from bacteria or viruses

stages of producing transgenic bacterium that can produce insulin

  1. Gene for human insulin is identified and cut out using a restriction enzyme

  2. Bacterial plasmids are extracted and cut open using the same restriction enzyme

  3. Plasmids and genes are mixed together and combined with ligase enzyme to form recombinant plasmids

  4. Bacteria is incubated with the recombinant plasmids to form genetically modified organisms with heat shock and calcium ions, they will now produce human insulin

  5. the GMO bacteria are grown in fermenters so they grow quickly through asexual reproduction.

  6. The insulin they produce is in the fermenter fluid and so is separated and purified

advantages

  • quick production of insulin

  • more ethical, available for people against using pig products

  • body is less likely to reject it - because it’s from the human gene

  • avoid possible disease from pig insulin

GMO Plants 5.15

Genetic modification in plants involve Agrobacterium tumefaciens (bacterium). This bacterium naturally infects plants and produces a tumour called a crown gall. It can be used as a vector for transferring useful genes into DNA of plant cells, creating GMO plants.

stages of genetically modifying plants

  1. Agrobacterium tumefaciens has Ti (tumor inducing) plasmid which cut with a restriction enzyme to use as a vector

  2. Desired gene is cut with the same restriction enzyme

  3. Ligase joins the gene and plasmid together

  4. Plasmids with the desired gene are put back into Agrobacterium tumefaciens

  5. The bacteria infects a plant/isolated leaf

  6. the plasmids cause production of a crown gall which contain cells with the desired gene

  7. Pieces of tissue are cut and grown into other plants with the desired gene

An advantage of this is famers can create herbicide resistant plants, meaning they can use heavier doses of herbicide to control weeds. However it could lead to resistant weeds, loss in biodiversity, or more invasive weeds replace the old ones.

This bacteria doesn’t infect all types of plants so instead they use a gene gun. small gold pellets covered in DNA with the desired gene are fired into the plant tissue. This genetically modified tissue can be grown into new plants via micropropagation.

Bacterial Insecticides

Soil Bacterium Bacillus thuringiensis produces a toxin called Bt ICP (Bt insecticidal crystal protein). The toxin kills a variety of insect pests including leaf eating caterpillars. Thuringiensis is inserted into the Ti plasmid of Agrobacterium. Crop plants infected with the GM bacterium develop crown gall. Pieces of gall tissue are then cultured and grown into plants that can produce their own Bt ICP toxin. The plants are able to resist insect attack.

Advantages

  • selective

  • harmless/no bioaccumulation

  • reduces harmful effects of insecticides - only affects insects feeding on the plant, so no need for insecticides which also saves money

Disadvantages

  • resistance

  • change food web

  • possible damage to human health

Transgenic Animals

Cloning can be used to produce transgenic animals, you can also just inject DNA into a newly fertilised egg cell.

Uses

  • Research - transgenic animals can be used to model for human disease which makes research for treatments easier

  • Drug production - transgenic animals can be used to produce human antibodies which are used as medicinal drugs

  • Xenotransplantation - transgenic animals can be genetically modified to produce organs which are suitable for human transplantation

  • Resistance - transgenic animals can be genetically modified to have increased resistance to disease and parasites

  • Higher Yield - transgenic animals can be genetically modified to increase production of a particular product like milk

Concerns/Problems

  • welfare of animals may be compromised

  • too expensive

  • unethical to change and use animals for our benefit

Risks of xenotransplantation

  • greater chance of immune rejection

  • transplanted organs may carry pathogens

  • hidden viruses in DNA could be passed to donor