Gene technology — Edexcel International A Level Biology
Making recombinant DNA, inserting it into cells, drugs from GMOs, microarrays, bioinformatics and the risks and benefits of GMOs.
Revision notes
5 short notes, in the order of the specification. Each one in short:
Recombinant DNA is DNA made by joining DNA from different sources. A restriction endonuclease cuts a gene and a plasmid vector at the same recognition sequence, leaving complementary sticky ends. These base-pair together and DNA ligase joins the sugar–phosphate backbones, forming a recombinant plasmid.
Recombinant DNA must enter host cells, which are then selected using marker genes. Bacteria take up plasmids after treatment with calcium chloride and a heat shock. In plants, Agrobacterium or a gene gun delivers the DNA, and in animals it is microinjected into a fertilised egg or delivered by a virus.
Genetically modified organisms can make human drugs. The human gene is inserted into a microorganism such as a bacterium or yeast, a plant or an animal, which makes the protein. Bacteria produce human insulin in fermenters, and transgenic animals and plants can make proteins in milk or leaves.
A microarray is a slide with thousands of spots of single-stranded DNA probes. mRNA from a cell is converted to labelled cDNA, which binds to matching probes; fluorescence shows which genes are active. Bioinformatics is the use of computers and software to store, analyse and interpret biological data such as DNA sequences.
Genetically modified organisms bring benefits and risks. They can increase crop yield, resist pests, improve nutrition and make medicines. Risks include transfer of genes to wild plants, effects on non-target organisms and biodiversity, possible health effects, cost and ownership of seeds, and ethical objections to modifying organisms.
Exam questions
8 exam-style questions (30 marks), each with its mark scheme.
Answer the questionsFlashcards
16 cards: flip them, mark what you knew, and practise the rest.
Practise the cardsMind map
The whole of coordination, response and gene technology on one page, so you can see where this subtopic fits.
Open the mind mapPrint it
Free PDFs to print or save.
Quick check questions
What is the role of a restriction endonuclease?
Show answer
It cuts DNA at a specific recognition sequence, leaving sticky ends.
What does DNA ligase do?
Show answer
It joins sugar–phosphate backbones of DNA fragments by forming phosphodiester bonds.
Why is a marker gene included in a plasmid?
Show answer
To identify the host cells that have taken up the plasmid.
What does a bright spot on a microarray show?
Show answer
That the gene with the matching probe is active, because mRNA from it was present.
What is bioinformatics?
Show answer
The use of computers and statistics to store and analyse large sets of biological data.
Frequently asked questions
How is recombinant DNA made?
A restriction endonuclease cuts the gene and a plasmid at the same recognition sequence, leaving complementary sticky ends. The gene and plasmid are mixed, so the sticky ends pair by complementary base pairing. DNA ligase then forms phosphodiester bonds between the sugar–phosphate backbones, producing a recombinant plasmid that can be put into a host cell.
What do restriction enzymes and DNA ligase do?
Restriction enzymes (restriction endonucleases) cut DNA at specific base sequences, hydrolysing phosphodiester bonds and often leaving single-stranded sticky ends. DNA ligase does the opposite job, forming phosphodiester bonds to join DNA fragments together. Together they allow a gene to be cut out and joined into a vector.
How are genes put into bacteria and plant cells?
Bacteria take up plasmids after treatment with calcium chloride and a heat shock, which makes their membranes permeable. Plant cells can be transformed by Agrobacterium, which transfers DNA from its Ti plasmid, or by a gene gun that fires DNA-coated metal particles into the cells.
How does a DNA microarray show which genes are active?
A microarray has thousands of spots of single-stranded DNA probes. Fluorescently labelled cDNA, made from a cell’s mRNA, binds to matching probes. After washing, spots that fluoresce show genes that were being transcribed, and brighter spots mean more mRNA. This identifies active genes in a tissue.
What are the risks and benefits of genetically modified organisms?
Benefits include higher yields, pest resistance, improved nutrition and large amounts of human proteins such as insulin. Risks include genes spreading to wild plants, harm to non-target organisms, loss of biodiversity, possible allergies, high seed costs and ethical objections. A judgement should weigh these using specific examples.
Written and checked against the Edexcel International A Level Biology (YBI11) specification · Updated October 2026