Genes are passed on from one generation to the next so that offspring inherit traits. Sections of DNA that contain messages are known as genes. The number of genes varies greatly between different species, with most higher animals and plants having anywhere from ten thousand to hundreds of thousands of genes. Genes can be switched on or off at different times and within different cells of the same organism. In most organisms, the long thread-like DNA molecules are organised within larger structures called chromosomes.
Genetic technologies aim to make a living thing perform a specific useful task.
This could be to fight disease, produce more food or simply to make a flower blue. Since the 1970s scientists have known how to manipulate genes, and how to transfer them from one species to another. A gene can now be isolated, rearranged, altered and joined to a new chromosome in another organism. This involves considerable expertise, expensive laboratory equipment and some remarkable scientific techniques, some of which are briefly outlined below. The original DNA is used as a template to make many copies.