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1.5Unit 1 — Cell Biology

Genetic Engineering

5 min read 4 parts Lesson 21 of 28

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Part 1 of 2Stages of genetic engineering

Production of human insulin using genetically modified bacteria
Recombinant plasmid: DNA ligase joins sticky ends
Production of human insulin by genetically modified bacteria
Industrial fermenter
recombinant dna
Inserting a gene into a plasmid using restriction enzyme and DNA ligase
Steps in Genetic Engineering
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Production of human insulin by genetic engineering
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Stage 1: Identification & Extraction
Stage 1: Identification & ExtractionThe required gene is identified on a source chromosome (e.g. human chromosome containing the insulin gene) and extracted using a specific restriction endonuclease enzyme.
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Stage 2: Plasmid Extraction & OpeningA circular plasmid vector is extracted from a bacterial host cell and cut open using the same restriction enzyme, ensuring compatible sticky ends.
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Stage 3: Insertion & Sealing
Stage 3: Insertion & SealingThe human gene is inserted into the cut open plasmid and permanently sealed into place using the enzyme DNA ligase to produce a recombinant plasmid.
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Stage 4: Transformation
Stage 4: TransformationThe recombinant plasmid is inserted into a host bacterial cell, creating a genetically modified (GM) bacterium.
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Stage 5: Fermentation & Purification
Stage 5: Fermentation & PurificationThe GM bacteria are cultured in large industrial fermenters under optimum growth conditions.
  • As they multiply rapidly, they express the introduced gene,
  • producing large quantities of the desired therapeutic protein,
    • (e.g. human insulin or human growth hormone)
  • which is then extracted and purified.

Part 2 of 2Applications and advantages

Restriction enzyme cuts DNA to form sticky ends
How restriction enzymes cut DNA
How restriction enzymes cut DNA
Restriction enzyme cutting DNA to form sticky ends
How restriction enzymes cut DNA
DNA Nucleotide
DNA Nucleotide
DNA Nucleotide
enzyme reaction cycle infographic
1Medical products produced by GM bacteria
  • Human insulinfor treating diabetes mellitus (eliminates allergic reactions associated with older animal-derived insulin).
  • Human growth hormone (HGH)for treating pituitary dwarfism in children.
  • Factor VIIIhuman blood clotting protein for treating haemophilia patients.
2Advantages of using microorganisms
  • Bacteria reproduce extremely rapidly under controlled conditions in fermenters.
  • Large volumes of identical, pure human proteins are produced at lower cost with zero risk of animal virus transmission.

Key terms

TermMeaning
Genetic engineeringThe artificial transfer of genetic information (DNA) from one organism into another.
PlasmidA small circular loop of bacterial DNA used as a cloning vector to transfer foreign genes.
Restriction enzymeAn enzyme that cuts DNA strands at specific recognition nucleotide sequences.
DNA ligaseAn enzyme that chemically joins and seals DNA fragments together.

Avoid these mistakes

Avoid these mistakes
Using different enzymes to cut the gene and plasmid — the same restriction enzyme must be used to ensure complementary sticky ends match.
Confusing the roles of restriction enzymes (cut DNA) and ligase (seals DNA together).
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