Skip to main content
SingaporeBiotechnologySyllabus dot point

How can adding a single gene make a crop resist pests, survive drought, or carry extra nutrients?

Describe how crops are genetically modified and discuss the benefits and concerns of GM crops

A focused answer to the O-Level outcome on GM crops. How a useful gene is inserted into a plant, examples such as pest resistance, and a balanced view of the benefits and concerns.

Generated by Claude Opus 4.89 min answer

Reviewed by: AI editorial process; not yet individually human-reviewed

Have a quick question? Jump to the Q&A page

Jump to a section
  1. What this dot point is asking
  2. The answer
  3. Examples in context
  4. Try this

What this dot point is asking

This outcome asks you to describe how crops are genetically modified and to discuss, in a balanced way, the benefits and concerns of GM crops. The technique is the recombinant DNA process applied to a plant, and the discussion is one of the clearest places examiners look for both sides of an argument.

The answer

What a GM crop is

A genetically modified (GM) crop is a plant that has had a useful gene from another organism inserted into it, giving it a new, helpful trait.

How a crop is genetically modified

The process applies recombinant DNA technology to a plant:

  1. Identify and cut out the useful gene, for example a gene that makes a protein toxic to a particular insect pest, using a restriction enzyme.
  2. Insert the gene into a vector, often a bacterium that naturally transfers DNA into plant cells, joining the gene with DNA ligase.
  3. Deliver the gene into plant cells, where it is incorporated and expressed.
  4. Grow the modified cells into whole plants, for example by tissue culture, so every cell of the new plant carries and expresses the gene and shows the trait.

Examples of useful traits

  • Pest resistance, so the crop is damaged less and needs fewer pesticides.
  • Herbicide tolerance, so weeds can be controlled without harming the crop.
  • Drought or salt tolerance, so crops grow in difficult conditions.
  • Added nutrients, such as extra vitamin A, to improve nutrition.

The benefits

GM crops can give higher yields, resist pests and diseases, reduce pesticide use, tolerate poor conditions, and improve nutrition, helping food security and farmers' incomes.

The concerns

There are worries about possible effects on health (though approved GM foods are tested), effects on the environment and other species (such as harm to non-target insects or genes spreading to wild plants), reduced biodiversity from growing single varieties, and farmers depending on a few large seed companies.

Examples in context

Example 1. Pest-resistant cotton. Cotton has been modified with a bacterial gene so it makes a protein toxic to a major insect pest. This reduces crop losses and the amount of insecticide sprayed, a widely grown example of GM in practice.

Example 2. Vitamin-enriched rice. Rice has been engineered to make extra vitamin A in the grain, aimed at reducing vitamin A deficiency in regions that rely on rice. It shows GM used to improve nutrition, while debate over its use shows the concerns side.

Try this

Q1. State what is meant by a genetically modified crop. [1 mark]

  • Cue. A crop plant that has had a useful gene from another organism inserted into it, giving it a new helpful trait.

Q2. Outline how a useful gene is introduced into a crop plant. [3 marks]

  • Cue. Cut out the gene with a restriction enzyme, join it into a vector (such as a bacterium that transfers DNA to plant cells) with ligase, deliver it into plant cells where it is expressed, and grow the cells into whole plants.

Q3. Give one benefit and one concern of GM crops. [2 marks]

  • Cue. Benefit: higher yield or pest resistance reducing pesticide use. Concern: possible environmental effects such as genes spreading to wild plants, or reduced biodiversity.

Exam-style practice questions

Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

Original6 marksDescribe how a crop plant can be genetically modified to carry a useful gene, such as one for pest resistance.
Show worked answer →

Examiners want the recombinant DNA process applied to a plant.

First, the useful gene is identified, for example a gene that lets a plant make a protein toxic to a particular insect pest. The gene is cut out using a restriction enzyme.

The gene is then inserted into a vector. A common method uses a bacterium that naturally transfers DNA into plant cells, or the gene may be introduced directly into plant cells. DNA ligase joins the gene into the vector to form recombinant DNA.

The vector carries the gene into plant cells, where it is incorporated and expressed. The modified cells are grown into whole plants, for example using tissue culture, so that every cell of the new plant carries and expresses the useful gene, giving it the desired trait such as pest resistance.

What markers reward: identifying and cutting out the useful gene, inserting it into a vector (such as a bacterium that transfers DNA to plants) with ligase, getting the gene into plant cells where it is expressed, and growing the cells into whole plants that carry the trait.

Original6 marksDiscuss the benefits and concerns of growing genetically modified crops.
Show worked answer →

The answer should give balanced benefits and concerns.

Benefits: GM crops can give higher yields, resist pests and diseases (reducing the need for chemical pesticides), tolerate drought or poor soils, and be enriched with nutrients (such as extra vitamins). This can improve food security and farmers' incomes and reduce chemical use.

Concerns: there are worries about possible effects on health, though approved GM foods are tested; about effects on the environment and other species, such as harm to non-target insects or the spread of genes to wild plants; about reduced biodiversity from growing single varieties; and about farmers depending on a few large companies for seed.

What markers reward: at least two benefits (such as higher yield, pest resistance, less pesticide, drought tolerance, added nutrients) and at least two concerns (such as health worries, environmental effects, gene spread, biodiversity, economic dependence), for a balanced discussion.

Related dot points