4.2.4 The Process of Genetic Engineering

• • The gene that is to be inserted is located in the original organism
  • Restriction enzymes are used to isolate the required gene, leaving it with ‘sticky ends’ (a short section of unpaired bases)
  • A bacterial plasmid is cut by the same restriction enzyme leaving it with corresponding sticky ends (plasmids are circles of DNA found inside bacterial cells)
• Restriction enzymes cut DNA strands at specific sequences to form ‘sticky ends’

  A) restriction

  
• DNA ligase is used to join two separate pieces of DNA together

  A) recombinant

  
• (1)

  • The plasmid and the isolated gene are joined together by DNA ligase enzyme
  • If two pieces of DNA have matching sticky ends (because they have been cut by the same restriction enzyme), DNA ligase will link them to form a single, unbroken molecule of DNA
• (2)

  • The genetically engineered plasmid is inserted into a bacterial cell
  • When the bacteria reproduce the plasmids are copied as well and so a recombinant plasmid can quickly be spread as the bacteria multiply and they will then all express the gene and make the human protein
  • The genetically engineered bacteria can be placed in a fermenter to reproduce quickly in controlled conditions and make large quantities of the human protein