At the cellular level, a clone is a population of cells derived from a single ancestor. All cells in a clone have the same genetic make-up.
The term clone may also refer to a lineage of genetically identical individuals derived from a single original parent by some form of asexual reproduction or by artificial propagation. Clones by arise naturally by parthenogenesis in animals. Cloning is often used in plant propagation (including tissue culture) to produce new plants from parents with desirable qualities such as high yield, or from plants which have been genetically engineered (see genetic engineering). It is now possible to produce animal clones from tissue culture. In 1997 scientists in Scotland announced that they had cloned a sheep. Using nuclear transfer (transfer of a cell nucleus) technology, they produced an embryo from a single udder cell of an adult sheep. The embryo was then implanted into a surrogate mother, and Dolly, an identical twin of the sheep that donated the cell, was born in February 1997. In 1998 Dolly gave birth naturally, thus allaying fears that, as a result of being cloned from an older sheep, she would not be able to reproduce. See also artificial selection.