Genetic engineering — Edexcel GCSE Combined Science
What genetic engineering is, and the main stages of the process using restriction enzymes, ligase and vectors.
Revision notes
2 short notes, in the order of the specification. Each one in short:
Genetic engineering is a process that modifies the genome of an organism to introduce desirable characteristics. Usually a gene is taken from one organism and inserted into an organism of a different species, making a genetically modified (GM) organism that can make the protein the gene codes for. For example, bacteria given the human insulin gene make insulin.
The main stages of genetic engineering
Higher tierIn genetic engineering, a restriction enzyme cuts the desired gene out of the donor DNA, leaving sticky ends. The same restriction enzyme cuts open a vector, such as a bacterial plasmid, giving matching sticky ends. The enzyme ligase joins the gene into the vector to make recombinant DNA, which carries the gene into the target organism's cells.
Exam questions
4 exam-style questions (10 marks), each with its mark scheme.
Answer the questionsFlashcards
7 cards: flip them, mark what you knew, and practise the rest.
Practise the cardsMind map
The whole of natural selection and genetic modification on one page, so you can see where this subtopic fits.
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Quick check questions
What is genetic engineering?
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Modifying the genome of an organism to introduce desirable characteristics.
What does a GM organism contain that a normal organism does not?
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A gene transferred from another organism.
Give one example of a desirable characteristic introduced by genetic engineering.
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For example, bacteria making human insulin, or crop plants resistant to insects.
Frequently asked questions
What is genetic engineering in agriculture?
In agriculture, genetic engineering means inserting a gene from another species into crop plants to give them a desirable characteristic. For example, crop plants can be given a gene for resistance to insect pests, so they are not damaged by the pest. The modified plants are called genetically modified (GM) crops.
How is human insulin made by genetic engineering?
Higher tier The human insulin gene is cut out of human DNA with a restriction enzyme, and a bacterial plasmid is cut with the same enzyme so the sticky ends match. Ligase joins the gene into the plasmid, which is then inserted into bacteria. The bacteria make human insulin, which is used to treat diabetes.
What is the difference between genetic engineering and selective breeding?
Selective breeding uses the genes already in a species, choosing parents with desired characteristics over many generations. Genetic engineering changes the genome directly, usually by inserting a gene from a different species. This makes genetic engineering quicker, and it can give an organism a characteristic coded for by another species' gene.
What are sticky ends in genetic engineering?
Higher tier Sticky ends are short, unpaired strands of DNA left at the ends of a cut made by a restriction enzyme. If the gene and the vector are cut with the same restriction enzyme, their sticky ends match. They join by complementary base pairing, and the enzyme ligase then joins the DNA strands together permanently.
Written and checked against the Edexcel GCSE Combined Science (1SC0) specification · Updated October 2026