20.3) Genetic engineering

20.3) Genetic engineering


Genetic engineering: is changing the genetic material of an organism by removing, changing or inserting individual genes.


Examples of genetic engineering:

  • The insertion of human genes into bacteria to produce human insulin.
  • The insertion of genes into crop plants to confer resistance to herbicides and insect pests.
  • The insertion of genes into crop plants to provide additional vitamins.


Bacterial production of a human protein such as insulin:

  1. Isolation of the DNA making up a human gene using restriction enzymes, forming sticky ends.
  2. Cutting of bacterial plasmid DNA with the same RE, forming complementary sticky ends.
  3. Insertion of human DNA into bacterial plasmid DNA using ligase enzymes to form a recombinant plasmid.
  4. Insertion of plasmid into bacteria.
  5. Replication of bacteria containing recombinant plasmid which make human protein as they express the gene.


  • Restriction enzymes cut DNA at specific sites, rather than just in random places along the DNA molecule. Eg. between the A and the T in the sequence GAA-TTC.
  • ligase enzymes join pieces of DNA together at specific sites.
  • The plasmids are said the be vectors that carry the human DNA into the bacteria and the techniques are sometimes called gene-splicing.
  • The bacteria are cultured in special vessels called fermenters and the insulin that they produce can be extracted from the culture medium and purified for use in treating diabetes.


Golden rice:


  • Produces beta carotene which is needed by humans in order to make vitamin A.
  • Used in areas where vitamin A deficiency is common, so it can help prevent night blindness.


  • beta carotene levels in golden rice may not be high enough to make a difference.
  • there are fears that it will cross-breed with and contaminate wild rice.
  • there are concerns that food from GM plants might harm people.
  • seed for GM plants can be expensive.


Soya and Maize:


  • Can contain pesticide residues or substances that causes allergies (allergens).


Herbicide-resistant crops:


  • The potential development of herbicide-resistant weeds.

Loss of biodiversity because fewer weeds survive – resulting in reduced food and shelter for animals.

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