Describe the process of transgenics, explaining how recombinant DNA is produced and then introduced into a host bacterial cell.

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

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

Model answer (4 marks)

1. Restriction enzymes cut the target gene from a donor chromosome, producing a DNA fragment with sticky ends.
2. The same restriction enzyme cuts a plasmid vector, creating compatible sticky ends.
3. DNA ligase joins the gene fragment to the plasmid, sealing the recombinant DNA.
4. The recombinant plasmid is introduced into a host bacterial cell, allowing the gene to be transferred and expressed.

Examiner tips

  • Use the exact terms: restriction enzymes, sticky ends, plasmid, ligase, recombinant DNA, host cell.
  • Show the sequence of steps in order.
  • Mention that the same enzyme creates compatible ends.
  • Keep the answer concise and to the point.

Common mistakes

  • Confusing blunt ends with sticky ends.
  • Omitting the role of ligase.
  • Failing to state that the same enzyme is used for both cuts.

Mark scheme (4 marks)

  1. Restriction enzymes are used to cut / isolate the desired gene from a chromosome
  2. The same restriction enzyme is used to cut open a plasmid (vector), producing compatible / sticky ends
  3. Ligase joins / seals the desired gene into the plasmid to produce recombinant DNA
  4. The plasmid (vector) is introduced into a host bacterial cell, transferring the recombinant DNA

Key terms in this question

transgenics · recombinant DNA

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