Explain how genetically modified bacteria are used to produce insulin for people with diabetes.

Pearson Edexcel International GCSE Biology (4BI1) — 5.3 Genetic modification (genetic engineering) · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Insulin is a hormone that controls blood glucose concentration. People with type 1 diabetes cannot produce sufficient insulin. Genetically modified bacteria grown in fermenters can be used to manufacture human insulin on a large scale.

Model answer (4 marks)

1. The human insulin gene is cut from human DNA using restriction enzymes.
2. The insulin gene is inserted into a plasmid (vector) to form recombinant DNA.
3. Ligase is used to join / seal the insulin gene into the plasmid.
4. The recombinant plasmid is transferred into bacteria, which are then grown in a fermenter to produce large amounts of insulin.

Examiner tips

  • Use the exact sequence of steps; list them in order.
  • Include key terms: restriction enzymes, plasmid, ligase, recombinant DNA, fermenter.
  • Show the purpose of each step briefly (e.g., ‘to insert the gene’).

Common mistakes

  • Mixing up the order of steps; e.g., putting ligase before restriction digestion.
  • Failing to mention the plasmid as the vector.
  • Not stating that bacteria are grown in a fermenter to produce insulin.

Mark scheme (4 marks)

  1. The human insulin gene is cut from human DNA using restriction enzymes
  2. The insulin gene is inserted into a plasmid (vector) to form recombinant DNA
  3. Ligase is used to join / seal the insulin gene into the plasmid
  4. The recombinant plasmid is transferred into bacteria, which are then grown in a fermenter to produce large amounts of insulin

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