Genetic modification

• Genetic engineering is a process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
• A transgenic organism contains genes transferred from another species by genetic engineering
• • The insulin gene is cut out of a section of human DNA using a restriction enzyme. These are highly specific so only cut either side of the gene and nowhere else
  • The same enzymes are used to cut open a plasmid from bacteria
  • The plasmid and gene is allowed to mix and joined using DNA ligase. The result is a plasmid containing both bacterial and human DNA. The DNA is known as recombinant
  • The plasmid is then placed into a bacterium, which is then allowed to divide. The resulting cells will all contain the plasmid as the DNA is copied every time. The bacteria is known as transgenic
• A vector is needed to 'carry' or transfer the genetic material into a cell.

  • Plasmids transfer the DNA into a bacterial cell
  • Viruses (e.g. bacteriophages) carry DNA into cells by infecting them, injecting DNA into the cell
• Examples of genetically modified plants:

  • Herbicide resistant
  • Drought resistant
  • Pest resistant
  • Disease resistant
  • Tomatoes that have a gene that keeps them ripe longer
  • More nutritious e.g. golden rice
  • Plants with scorpion venom gene to deter herbivores
  • Bigger yields
  • Frost resistant
• • Scientists extract plasmids from bacteria and insert the useful foreign gene
  • DNA ligase is used to join the two pieces of DNA together and the result is a recombinant plasmid
  • The recombinant plasmid is then inserted into bacteria
  • The bacteria are mixed with the plant cells
  • Some of the plasmids are able to enter the plant cells and become part of the plant chromosome in the nucleus
  • These pant cells are now transgenic as they contain the DNA from another species
  • The plants can then be cloned to make more of them
• Scientists can use a bacteria called Argobacterium tumefaciens. This is a natural pathogen that inserts its plasmid into the nucleus of the plant. The DNA then incorporates into the plant chromosome. Therefore, they can be used as vectors
• Positives:

  • Resistance to pests means less pesticides need to be used
  • Better nutritional value
  • Higher yield could solve world hunger
  • Longer shelf life means less food wastage
• Negatives:

  • The GM plant might crossbreed and contaminate wild populations with the foreign DNA
  • Expensive to produce - food costs increase
  • GM foods might have harmful long-term effects on humans