Explain why bacteria are considered particularly useful organisms for producing human insulin by genetic modification.

Cambridge International IGCSE Biology (0610) — 21.3 Genetic modification · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

1. Bacteria reproduce rapidly, allowing large quantities of insulin to be produced quickly.
2. Bacteria possess plasmids, circular DNA molecules that can carry the inserted human insulin gene.
3. The insulin gene can be expressed in bacteria, so they produce the human insulin protein.
4. There are no ethical concerns about manipulating bacterial DNA, unlike with human or animal cells.

Examiner tips

  • Use the exact wording from the mark scheme, e.g. "reproduce rapidly" and "plasmids". Include all four points in separate sentences. Show the logical link between each point and insulin production.

Common mistakes

  • Using vague terms like "fast growth" instead of "reproduce rapidly". Omitting the point about ethical concerns. Mixing up plasmids with chromosomes.

Mark scheme (4 marks)

  1. Bacteria reproduce very rapidly, so large quantities of insulin can be produced quickly.
  2. Bacteria contain plasmids, which are circular pieces of DNA that can be used to carry the inserted human insulin gene.
  3. The insulin gene can be expressed in bacteria, so the bacteria produce human insulin protein.
  4. There are no ethical concerns about manipulating bacterial DNA, unlike with human or animal cells.

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