Describe how genetic engineering could be used to produce bacteria that make human insulin.

Edexcel GCSE Biology (1BI0) — 4.3 Selective breeding and genetic engineering · Describe · 4 marks · View as Markdown

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

People with type 1 diabetes cannot produce insulin. Genetic engineering can be used to produce human insulin on a large scale using bacteria.

Model answer (4 marks)

1. The human insulin gene is excised from human DNA with restriction enzymes.
2. The enzymes create compatible sticky ends on the insulin gene and on a plasmid vector.
3. The gene is inserted into the plasmid and joined with DNA ligase to form recombinant DNA.
4. The recombinant plasmid is introduced into bacteria, which then produce human insulin.

Examiner tips

Use the exact sequence of steps: cut, sticky ends, insert, ligase, transform.
Show the role of restriction enzymes and ligase.
Mention the plasmid as the vector.
Keep the answer concise and in order.

Common mistakes

Omitting the role of restriction enzymes or ligase.
Using vague terms like ‘insert’ without explaining sticky ends.
Listing steps out of order or missing the plasmid vector.

Mark scheme (4 marks)

The human insulin gene is cut from human DNA using restriction enzymes
The restriction enzymes create sticky ends on the insulin gene (and the vector/plasmid DNA)
The insulin gene is inserted into a vector (plasmid) and joined using ligase to form recombinant DNA
The recombinant plasmid is introduced into bacteria, which then produce human insulin

Key terms in this question

genetic engineering