Copyright © 2007 Dorling Kindersley
Plant crops provide us with food, clothing, and many other important products. Farmers select seeds from the best plants to grow next season. This selective breeding makes plants evolve features that people want them to have – such as heavier rice grains – but it is a slow process. To change faster, crops can be given new features directly from other life forms. Cells take their features from instructions they carry, called genes. Genetic modification (GM) allows us to move a gene from one life form to another.
In genetic modification, scientists first identify the gene for the desired feature. They can cut this donor gene from its DNA strand, using chemicals called enzymes as scissors. The gene is kept in one piece and multiplied by inserting it into a bacterium. The bacterium is used to carry the new gene into the target plant, by “infecting” it.
Scientists use plasmids, which are found inside bacteria, to stop donor genes unravelling and to replicate (copy) them. The donor gene is zipped on to the plasmid using chemicals called enzymes.
Tomatoes can be bruised when they are packed and stored. As they ripen, their skins become more delicate and are more easily damaged. Damaged tomatoes quickly begin to rot, because mould can grow on their skins. Scientists have genetically modified tomatoes by adding genes that stop their skins softening as they ripen. This means they are less likely to bruise in storage and be wasted.