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How do humans change organisms through selective breeding and genetic engineering?

The process of selective breeding and its risks, the process of genetic engineering and its uses, including genetically modified crops and the production of human insulin, and the ethical issues raised.

A focused answer to AQA GCSE Biology 4.6.2.3 to 4.6.2.4, covering selective breeding and its risks, the process and uses of genetic engineering including GM crops and human insulin, and the ethical issues raised.

Generated by Claude Opus 4.810 min answer

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

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  1. What this dot point is asking
  2. Selective breeding
  3. Genetic engineering
  4. Uses of genetic engineering
  5. Benefits, risks and ethics
  6. Try this

What this dot point is asking

AQA wants you to describe selective breeding and its risks, explain the main steps of genetic engineering, give its uses (such as GM crops and producing human insulin), and discuss the benefits, risks and ethical concerns.

Selective breeding

Examples include cows that produce more milk or beef, crops with disease resistance or higher yields, dogs with a gentle nature for use as pets or working animals, and large or unusually coloured flowers. Selective breeding has been used by farmers for thousands of years, long before genes were understood.

Genetic engineering

The general steps:

  1. The required gene is cut out of the chromosome using enzymes.
  2. The gene is inserted into a vector, usually a bacterial plasmid or a virus, which is also cut with enzymes so the gene fits in.
  3. The vector transfers the gene into the cells of the target organism. In plants and animals this is done at an early stage of development, so that all the cells of the mature organism carry the new gene and show the new characteristic.

Uses of genetic engineering

Producing human insulin in bacteria is a key example: the bacteria multiply rapidly, so large amounts of insulin can be made cheaply, and because it is human insulin it works well and is less likely to cause a reaction.

Benefits, risks and ethics

GM crops can increase yields and improve nutrition, helping food supply, but concerns include possible effects on wild flowers and insects and so on biodiversity, uncertainty about long-term health effects of eating GM food, and the ethical question of whether it is right to alter the genes of organisms. These economic, social and ethical issues are widely debated, and AQA may ask you to weigh them up.

Try this

Q1. Describe one risk of selective breeding. [2 marks]

  • Cue. It reduces the gene pool (inbreeding), so the population is more likely to suffer from inherited diseases.

Q2. Give one use of genetic engineering. [1 mark]

  • Cue. Producing human insulin from bacteria (or making pest-resistant GM crops).

Exam-style practice questions

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

AQA 20194 marksDescribe how a farmer would use selective breeding to produce a herd of cows that all give a high yield of milk, and explain one risk of selective breeding.
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A 4-mark question rewards the method over generations plus a risk.

The farmer chooses the cows that produce the most milk and the bull from a high-milk-yield line, and breeds them together. From the offspring, the farmer again selects those with the highest milk yield and breeds them. This is repeated over many generations until all the offspring give a high milk yield.

A risk is that selective breeding reduces the gene pool (the variety of alleles), leading to inbreeding. This makes the herd more likely to inherit disease and less able to survive a new disease or change in conditions, because there is less variation.

Markers reward choosing the best individuals, breeding them and repeating over generations, and reduced gene pool or inbreeding as the risk.

AQA 20214 marksBacteria can be genetically engineered to produce human insulin. Describe the main steps of genetic engineering, and give one advantage of producing insulin this way.
Show worked answer →

A 4-mark question rewards the steps plus a benefit.

The gene for human insulin is cut out of a human chromosome using enzymes. The gene is inserted into a vector, such as a bacterial plasmid (also cut with enzymes). The vector carrying the gene is then put into bacteria, which are cultured so they multiply and make large quantities of human insulin, which is collected and purified.

An advantage is that large amounts of human insulin can be produced quickly and cheaply, and it is identical to human insulin so it is less likely to cause an immune reaction than insulin from animals.

Markers reward cutting out the gene with enzymes, inserting it into a vector (plasmid), putting it into bacteria, and an advantage such as a large supply of human insulin.

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