A clone is a biological duplicate of a living organism down to the genetic level. The cultivated organism is developed using macromolecular DNA that originates from the source. The science and study of clone structure is called cloning. The clone organism may be something as small as a strand of DNA, an organ, a limb and up to and including entire life forms such as people and animals. In many cases, clones are genetically modified so that they age at an accelerated rate. In other examples, clones may be created by mixing genetic material from what would otherwise be considered incompatible sources. Clones are a popular storytelling convention in science fiction and have been used in nearly all aspects of the medium.
In the 1997 sci-fi/horror film Alien Resurrection, genetic material preserved from the late human Ellen Ripley was combined with that of an alien Xenomorph to create a humanoid with an alien's agility and predatory instincts.