Edexcel IGCSE Biology

Revision Notes

5.3.1 The Process of Genetic Engineering

Higher Tier Only

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, IGCSE & GCSE Biology revision notes

Restriction enzymes cut DNA strands at specific sequences to form ‘sticky ends’

  • 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

Recombinant plasmids, IGCSE & GCSE Biology revision notes

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

  • 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

Author: Lára

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.
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