How do humans deliberately change the characteristics of living things?
Selective breeding and its uses and risks, genetic engineering and the steps involved, the use of genetically modified organisms, and the benefits and concerns of GM technology.
A focused answer to Edexcel GCSE Combined Science Topic 4 (CB4), covering selective breeding and its uses and risks, the steps of genetic engineering, the use of genetically modified organisms, and the benefits and concerns of GM technology.
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What this dot point is asking
Edexcel wants you to describe selective breeding with its uses and risks, describe the main steps of genetic engineering, explain how genetically modified organisms are used, and evaluate the benefits and concerns of GM technology.
Selective breeding
It is used to produce cows with high milk yield, crops with disease resistance, dogs with gentle temperaments, and large or unusual garden plants. The method is always the same: select the best individuals, breed them, select the best offspring, and repeat.
Genetic engineering
Genetic engineering (genetic modification) transfers a gene from one organism into the genome of another, so it produces a desired protein or characteristic. The main steps are:
- The gene for the desired characteristic is cut out (isolated) using enzymes.
- The gene is inserted into a vector (often a plasmid or a virus).
- The vector transfers the gene into the cells of the target organism.
- The modified organism then expresses the new gene.
A classic example is inserting the human insulin gene into bacteria, which then make human insulin for treating diabetes. Crops have been modified to resist insect pests or herbicides, or to add vitamins (for example golden rice, enriched with vitamin A).
Benefits and concerns of GM
GM technology can give higher yields, pest and disease resistance, better nutrition, and the production of useful medicines. Concerns include possible effects on biodiversity (harming non-pest insects), the spread of inserted genes to wild plants, ethical worries, and uncertainty about long-term effects on health and the environment.
Try this
Q1. State one risk of selective breeding. [1 mark]
- Cue. Reduced variation, or making harmful recessive alleles more common (inbreeding problems).
Q2. Name one useful product made by genetically modified bacteria. [1 mark]
- Cue. Human insulin.
Exam-style practice questions
Practice questions written in the style of Pearson Edexcel exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
Edexcel 20204 marksDescribe how a farmer could use selective breeding to produce cows that give more milk.Show worked answer →
A 4-mark describe question that must show the cycle repeated over generations.
Choose (select) the cows that already produce the most milk and breed them together (1 mark). From their offspring, again select the ones that produce the most milk and breed them (1 mark). Repeat this process over many generations (1 mark). Over time the average milk yield of the herd increases, because the alleles for high milk yield become more common (1 mark).
Markers reward selecting the best parents, breeding them, and crucially repeating over many generations. A common error is to describe only one round of breeding.
Edexcel 20224 marksGenetically modified crops can be made resistant to insect pests. Explain one benefit and one concern of growing genetically modified crops.Show worked answer →
A 4-mark evaluate-style question needing a benefit and a concern, each explained.
Benefit: insect-resistant GM crops need fewer pesticide sprays and give a higher yield, so more food can be produced from the same land and farmers spend less on chemicals (2 marks). Concern: there are worries that GM crops could affect biodiversity (for example harming insects that are not pests), that the inserted genes could spread to wild plants, or about possible long-term effects on human health that are not yet fully known (2 marks).
Markers reward a clearly explained benefit and a clearly explained concern, not just one-word answers.
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Sources & how we know this
- Edexcel GCSE (9-1) Combined Science (1SC0) specification — Pearson (2016)