🌾 Plant crops
Crops have been genetically engineered to be resistant to diseases, to be resistant to insect attack or to herbicides, or to produce bigger, better fruits.
Variation and Evolution » Genetic Engineering
What you'll learn this session
Study time: 30 minutes
AQA spec: 4.6.2.4
- What genetic engineering is and what GM crops are
- How crops and bacteria have been genetically engineered
- The benefits, risks and objections in agriculture and medicine
- Higher tier: the main steps in genetic engineering
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Unlock This CourseWhat is genetic engineering?
In the last lesson, humans chose which plants and animals to breed. That takes many generations. Genetic engineering is much more direct. Scientists change the genes of an organism itself.
Genes from the chromosomes of humans and other organisms can be 'cut out' and transferred to the cells of other organisms. The new gene gives the organism a desired characteristic.
Key terms:
- Genetic engineering: a process which modifies the genome of an organism by introducing a gene from another organism to give a desired characteristic.
- Genetically modified (GM) crop: a crop that has had its genes modified in this way.
What has been genetically engineered?
🦠 Bacterial cells
Bacteria have been genetically engineered to produce useful substances. A good example is human insulin, which is used to treat diabetes.
GM crops generally show increased yields. A yield is the amount of crop that a farm produces. A crop that is not damaged by insects or disease gives more food from the same field.
A herbicide kills plants. A crop that is resistant to a herbicide survives when the herbicide is sprayed on the field, but the weeds around it do not.
Genetic engineering in medicine
Insulin made by genetically engineered bacteria is human insulin. People with diabetes use it as a treatment, as you saw in the lessons on blood glucose and diabetes.
Modern medical research is also exploring the possibility of genetic modification to overcome some inherited disorders. You met inherited disorders earlier in this topic. The idea is to change the genes so that the disorder no longer happens. This is still being researched, so it is not yet an established treatment.
The main steps (Higher tier only)
Higher tier only
You must be able to describe the main steps in the process of genetic engineering.
- Enzymes are used to isolate the required gene.
- The gene is inserted into a vector. The vector is usually a bacterial plasmid or a virus.
- The vector is used to insert the gene into the required cells.
- Genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development, so that they develop with the desired characteristics.
A vector is the carrier that moves the gene into a new cell. Think of it as a delivery van for the gene. Doing this at an early stage of development means that every cell of the organism grows from a cell that already has the new gene.
Worked example (Higher tier only)
Question: put these steps for making a GM crop in order. (A) The vector inserts the gene into plant cells. (B) The gene is put into a vector. (C) Enzymes isolate the gene for insect resistance.
Answer: C, B, A. First the gene is isolated, then it goes into the vector, then the vector moves it into the cells.
Benefits, risks and objections
You must be able to explain the potential benefits and risks of genetic engineering in agriculture and in medicine, and know that some people have objections.
✅ Potential benefits
GM crops generally show increased yields, so more food can be grown. Crops resistant to disease or insects lose less to pests. Bacteria can make useful substances such as insulin. Research may help to overcome some inherited disorders.
⚠ Potential risks
GM crops may affect populations of wild flowers and insects. Some people feel the effects of eating GM crops on human health have not been fully explored.
Some people have objections to genetic engineering. They may be worried about the effects on wild flowers and insects, or about the effects of eating GM crops on human health, which have not been fully explored.
Common mistakes
Genetic engineering is not the same as selective breeding. Selective breeding picks parents that already have the characteristic. Genetic engineering moves a gene from one organism into another. Do not say that GM crops are proven to be harmful to health. The spec says the effects have not been fully explored.
Exam-style question
A farmer wants to grow a GM crop that is resistant to insect attack.
(a) Describe what is meant by genetic engineering. [2 marks]
(b) Give one benefit and one concern of growing GM crops. [2 marks]
(c) Higher tier: describe the main steps used to make the GM crop. [4 marks]
Model answer
(a) Modifying the genome of an organism (1) by introducing a gene from another organism to give a desired characteristic (1).
(b) Benefit: increased yield, or less loss to insects (1). Concern: it may affect populations of wild flowers and insects, or the effects of eating GM crops on human health have not been fully explored (1).
(c) Enzymes are used to isolate the required gene (1). The gene is inserted into a vector, such as a bacterial plasmid or a virus (1). The vector is used to insert the gene into the required cells (1). The genes are transferred at an early stage of development so the plant develops with the desired characteristic (1).
Exam tip
For a 'benefit and concern' question, give one of each and be specific. Say 'increased yield' or 'effect on wild flowers', not just 'good' or 'bad'.