Genetic modification

Genetic engineering changes an organism’s genome by adding a useful gene from another organism. Enzymes cut the gene out, a vector such as a bacterial plasmid carries it into the new cells, and the organism then makes the protein the gene codes for. Bacteria make human insulin this way, and GM crops can resist pests or make extra vitamins. People weigh these benefits against concerns about safety and the environment.

Key facts

  • Genetic engineering changes an organism's genome by adding a gene from another organism. Bacteria have been given the human insulin gene, and crops have been given genes to resist insect pests or weedkillers or to make more vitamins.
  • The steps: enzymes cut the gene out; it is inserted into a vector, such as a bacterial plasmid or a virus; the vector carries it into the target cells. In plants and animals the gene is put in at an early stage, so all the cells get it.
  • Concerns about GM organisms include genes spreading to wild plants, effects on insects and wild flowers, unknown long-term effects on health, and whether it is right to change genes.
  • Gene therapy aims to treat inherited disorders by putting a working allele into a patient's cells.

Worked examples

Example 1

What is genetic engineering?

  1. A useful gene is cut from one organism and inserted into another.
  2. The organism then has a characteristic it did not have before.

Answer: changing the genome of an organism by putting in a gene from another organism

Example 2

Put the steps of genetic engineering in order.

  1. Enzymes cut the useful gene out of the DNA.
  2. The gene is inserted into a vector such as a bacterial plasmid.
  3. The vector carries the gene into the cells of the target organism.
  4. The organism makes the protein coded for by the new gene.

Answer: enzymes cut the gene out → it is put into a vector such as a plasmid → the vector carries it into the cells → the organism makes the protein

Example 3

Describe how bacteria can be engineered to make human insulin.

  1. Enzymes cut the insulin gene out of human DNA.
  2. A plasmid is cut open with the same enzymes and the gene is inserted (joined in by ligase).
  3. The plasmid, the vector, is put back into a bacterium.
  4. The bacteria multiply in a fermenter and make human insulin.

Answer: enzymes cut out the insulin gene; it is put into a plasmid; the plasmid is taken up by bacteria, which then make insulin

Example 4

Which technique produced these: rice given genes so that it makes a substance the body turns into vitamin A?

  1. A gene was moved from one organism into another.
  2. So this is genetic engineering.

Answer: genetic engineering

Example 5

Which of these is a benefit of genetic engineering?

  1. Benefit: crops with higher yields.

Answer: crops with higher yields

Example 6

Which of these is a concern about GM crops?

  1. Concern: genes from GM crops could spread to wild plants.

Answer: genes from GM crops could spread to wild plants

Example 7

Give one advantage and one disadvantage of GM crops.

  1. Advantage: crops resistant to insects or disease give bigger harvests and need fewer pesticides.
  2. Advantage: crops such as golden rice can add vitamins to people's diets.
  3. Disadvantage: the new genes could spread to wild relatives by pollen.
  4. Disadvantage: some people worry about long-term effects on health and wildlife.

Answer: advantage: higher yields or resistance to pests; disadvantage: genes could spread to wild plants, and effects are not fully known