Crops that have had their genes modified in this way are called genetically…

The idea

A genetically modified crop is a plant whose genetic material has been changed by genetic engineering rather than by selective breeding. The change is made by cutting a useful gene from a donor organism and inserting it into a plant cell, often using a plasmid or a gene gun. The plant cell is then grown into a whole plant, so every cell contains the new gene. Because the gene is present in the plant's cells, the plant can make the protein coded for by that gene.

For example: A gene for a natural insect-killing protein can be transferred into maize, making the maize plant able to kill insect pests that feed on it.

What earns the marks

• GM stands for genetically modified.
• A GM crop has had its DNA altered by genetic engineering, not by selective breeding.
• The inserted gene comes from another organism and is passed on as the plant grows and reproduces.
• The plant expresses the new gene by making the protein it codes for.
• The modification gives the crop a new characteristic, such as pest resistance.
• The term GM crop applies to any crop plant produced by this gene-transfer method.

Common mistakes and how to put them right

• Confusing GM crops with crops produced by selective breeding.

  Put it right: Selective breeding chooses existing variants, whereas genetic engineering inserts a gene from another organism.

• Thinking only the treated plant cell is modified.

  Put it right: The whole plant grown from that cell contains the new gene.

• Assuming GM always means the crop is harmful.

  Put it right: The term only describes how the crop was produced.

Exam tips

• Define GM in one clear sentence before giving an example.
• Use the phrase genetically modified in full at least once, then the abbreviation GM.
• Contrast GM with selective breeding to show you understand the difference.