Genetic engineering in plant crops
Laura Armstrong & Joe Wolfensohn
Teachers
Recall Questions
This topic requires prior knowledge of genetic engineering.
What is a herbicide?
A weedkiller.
What is a plasmid?
A small circular piece of DNA found in bacteria.
How are genes cut from DNA?
Using enzymes.
Topic Explainer Video
Check out this @JoeDoesBiology video that explains genetic engineering in plant crops, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
What Is Genetic Engineering?
Genetic engineering is the process of modifying the genome of an organism by inserting a gene from another organism to give a desired characteristic.
-
Used in agriculture (e.g. disease-resistant crops)
-
Used in medicine (e.g. insulin production by bacteria). See previous study note for more on this.
Examples of Genetic Engineering in crops
Crops may be genetically modified to have the following useful traits. These crops would be described as GM (genetically modified) crops:
-
crops resistant to diseases / pests.
-
crops resistant to frost.
-
crops resistant to drought.
-
crops / foods with added nutrients.
-
crops with more / bigger fruits or higher yield.
-
crops with improved taste.
-
crops with improved shelf life.
Steps in Genetic Engineering – Re-cap
In genetic engineering, genes from the chromosomes of humans and other organisms can be ‘cut out’ and transferred to cells of other organisms.
Higher tier only
-
Use enzymes to cut out the desired gene from DNA.
-
Insert the gene into a vector (e.g. plasmid or virus).
-
Insert the vector into the target cells (such as bacterial cells).
Example - genetically modifying a crop plant to be herbicide resistant.
-
Identify the gene that gives herbicide resistance (usually from a bacterium).
-
Use enzymes to cut out this gene from the DNA.
-
Insert the gene into a vector (commonly a plasmid or virus).
-
Use the vector to transfer the gene into plant cell DNA (e.g. wheat or maize).
-
The modified plant cells are grown to produce adult plants.
-
The gene is transferred at an early stage of development, so all new cells carry the new trait. (All new cells are made by mitosis so will be genetically identical).
-
These plants now grow with resistance to herbicide.
No answer provided.
Benefits of Herbicide-Resistant Crops
-
Farmers can spray herbicides to kill weeds without damaging the crop.
-
This means there is less competition from weeds for light, water and mineral ions → crops grow better and faster.
-
Higher crop yields → more food production → more financial gain for the farmer.
-
Reduces need for manual weeding or multiple chemical sprays.
Benefits of GM crops
-
Improved crop yield.
-
Reduced need for herbicides / pesticides which is better for the environment. It is also less time consuming for the farmer.
-
With increased crop yield comes more profit for the farmer and more food to feed a growing population.
-
Food can also be made to have more nutritional value by using genetic modification.
Risks and Concerns of GM crops
-
May reduce biodiversity (e.g. harming insects or wildflowers).
-
Some people worry about long-term health effects of eating GM foods.
-
Risk of inserted genes being transferred to wild plants and damaging food chains.
-
GM seeds are more expensive to buy for farmers.
Key Terms
-
Genetic engineering – Modifying DNA to give an organism a desired trait.
-
GM crops – Plants that have had genes inserted to improve their characteristics.
-
Plasmid – A small loop of DNA in bacteria, often used as a vector.
-
Vector – A mechanism used to transfer DNA into cells (e.g. plasmid or virus).
-
Herbicide – Weed killer.
-
Pesticide – Chemical use to kill pests such as insects that may eat and damage a crop plant.
-
Yield – Amount of crop produced.
No answer provided.
Exam Tips
- Always explain the benefit of genetic modification.
- For high-tier questions, include the use of enzymes and vectors.
- Remember if genetically modifying a plant, it must be done at an early stage of development, so all cells of the plant will contain the new gene.
No answer provided.
Practice Questions
Question 1
Insects can be both useful and harmful to crop plants.
Insects such as bees pollinate the flowers of some crop plants. Pollination is needed for successful sexual reproduction of crop plants.
Some insects eat crops and other insects eat the insects that eat crops.
Corn borers are insects that eat maize plants.
A toxin produced by the bacterium Bacillus thuringiensis kills insects.
Scientists grow Bacillus thuringiensis in large containers. The toxin is collected from the containers and is sprayed over maize crops to kill corn borers.
A company has developed genetically modified (GM) maize plants. GM maize plants contain a gene from Bacillus thuringiensis. This gene changes the GM maize plants so that they produce the toxin.
Describe how scientists can transfer the gene from Bacillus thuringiensis to maize plants. (5 marks)
gene cut out
from bacterial chromosome / DNA
using enzymes
gene inserted into maize chromosome / DNA
(gene added) at an early stage of development.
Question 2
Would you advise farmers to grow GM maize plants?
Justify your answer by giving advantages and disadvantages of growing GM maize plants.
Use the information from the text and your own knowledge to help you. (4 marks)
Advantages:
- less effort for farmer.
- pesticide always there or doesn’t wash away.
- allow examples eg. no need to spray pesticides.
- fewer insects to eat crop / maize.
- so greater crop production / yield.
Disadvantages:
- Toxin kills other insects.
- so crops may not get pollinated.
- possible harm when eaten by humans / animals.
- crop may have unpleasant taste.
- damage to food chains.
- reduced biodiversity.
- gene may spread to other species.
More Practice
Try to answer these practice questions from the TikTok videos on your own, then watch the videos to see how well you did!