HL 1 Biology

4.4a Transgenic Techniques


Biotechnology: modern forms of industrial production using living organisms

Genetic engineering: group of techniques developed by molecular biologist that allow genes to transfer between species

Genetic modification: transfer of genes from one species to another (used to produce new crop plants)

<<Gene Transfer>>

  • genes can transfer to another species using variety of techniques
  • common gene transfer to bacteria: involving plasmids, restriction enzymes and DNA ligase
  • plasmid: small extra circle of DNA
    • used in bacteria to exchange genes
  • restriction enzymes: enzymes which cut DNA molecules at specific base sequences
    • can cut open plasmids
    • can cut two strands of DNA molecule at different points = producing sticky ends, which have complementary base sequences that can link together pieces of DNA using hydrogen bonding
  • DNA ligase: enzyme that joins DNA molecules by making sugar-phosphate bonds between nucleotides
  • Requirement for gene transfer = a copy of gene being transferred (reverse transcriptase: enzyme that makes DNA copies of RNA molecules, cDNA)

<<Examples of Genetic Modification>>

  • e.g. gene transfer for making human insulin (genetic modification of bacteria)
  • Goats genetically modified to secrete an anti-clotting agent (anti-thrombin) in milk
  • Sheep genetically modified to make alpha-1-antitrypsin (protein)
  • Crop plants: produce protein which allows them to be resistant to herbicide glyphosphate
  • Golden rice: intended to solve issue of vitamin A deficiency (cause of child blindness)
  • developing genetically modified organisms is expensive, thus only performed for clear benefits
  • e.g. Enviropig: genetically engineered with DNA from E. coli and help digest the phosphorous absorbed by the pig

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