A gene is a code that governs our appearance and characteristics. When a scientist genetically modifies (GM) a plant, s/he inserts a foreign gene in the plant’s own genes. What makes it possible to transfer genes from one species to another is the fact that all genes are created from the same material DNA. Beneficial genes are transferred into plant cells using a soil bacterium, Agrobacterium tumefaciens, which can produce tumour-like growths in plants and has the ability to alter plants’ DNA. For example, when a gene from a bacterium that is resistant to pesticide is inserted into a plant’s gene, the plant will be able to withstand pesticides. Genetic modification does not always involve moving a gene from one organism to another. Sometimes it means changing how a gene works by ‘switching it off’ to stop something from happening. For example, the gene for softening a fruit could be switched off so that although the fruit ripens in the normal way, it will not soften as quickly. This can be useful because it means that damage is minimised during packing and transportation.