Genetically modified plants

Use of biological resources · Selective breeding and genetic modification · note 4 of 4

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Genetically modified plantsSpec 5.15

In short

Genetically modified plants have a gene for a useful characteristic transferred into them to improve food production. For example, a gene from the bacterium Bacillus thuringiensis codes for Bt toxin, which kills insect pests, so the crop has insect resistance. This raises yields and reduces insecticide use, but genes may spread to wild plants.

Genetically modified plants can be used to improve food production. A gene for a useful characteristic is transferred into a crop plant, so the crop has that characteristic.

A well-known example is the gene from the bacterium Bacillus thuringiensis (Bt) put into crop plants. The gene codes for a toxin that kills many insect pests. The plants make the toxin themselves and so have insect resistance.

Advantages and disadvantages of GM crops
Advantages	Disadvantages
Less crop is lost to pests, so yields are higher	Possible risk to human health, which some people worry about
Less insecticide needs to be sprayed, which saves money and reduces damage to other organisms	Genes may spread to wild plants, and the toxin might harm other insects
Crops can be given extra characteristics, such as greater nutritional value or resistance to disease	GM seeds can be expensive
More food can be produced for a growing population	Concerns that it is wrong or unnatural to change the genes of organisms

Exam tip:

Structure 'advantages and disadvantages' answers as a balanced argument. Link each point to the crop, the farmer, people or the environment.

Quick check

What is selective breeding?
Show answer
Humans choosing which organisms to breed so that desired characteristics are passed on to the next generation.
Which enzyme cuts DNA at specific sites?
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A restriction enzyme.
Which enzyme joins pieces of DNA together?
Show answer
Ligase.
What does transgenic mean?
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The transfer of genetic material from one species to a different species.
Where are GM bacteria grown to make large amounts of insulin?
Show answer
In a fermenter.

Written and checked against the Edexcel IGCSE Biology (4BI1) specification · Updated October 2026

Frequently asked questions

What is selective breeding in plants?

Selective breeding in plants is when humans choose parent plants with a desired characteristic, such as disease resistance, larger grains or higher yield, and breed them together. The offspring that show the characteristic most strongly are bred again, and this is repeated over many generations until the characteristic is strongly shown in the variety.

What are the disadvantages of selective breeding?

Selective breeding reduces genetic variation, because only a few individuals are used for breeding. If a new disease or a change in the environment appears, all individuals may be affected. Breeding closely related individuals, called inbreeding, can also make harmful inherited conditions more common in domesticated animals.

What is genetic engineering in agriculture?

Genetic engineering in agriculture is transferring a gene for a useful characteristic from one species into a crop plant, making a genetically modified plant. For example, a gene from Bacillus thuringiensis makes crops produce Bt toxin, which kills insect pests. This gives higher yields and less insecticide use, though genes may spread to wild plants.

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