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:
- Isolation of the DNA making up a human gene using restriction enzymes, forming sticky ends.
- Cutting of bacterial plasmid DNA with the same RE, forming complementary sticky ends.
- Insertion of human DNA into bacterial plasmid DNA using ligase enzymes to form a recombinant plasmid.
- Insertion of plasmid into bacteria.
- 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.
- 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).
- The potential development of herbicide-resistant weeds.
Loss of biodiversity because fewer weeds survive – resulting in reduced food and shelter for animals.