Cloned Organisms, Eukaryotic

A cloned organism is defined as one that is derived by asexual reproduction from, and is genetically identical to, a multicellular parental organism. Cloning of animals from somatic cells involves the transfer of donor nuclei into enucleated egg cytoplasm. Epigenetic reprogramming of the somatic nuclei by factors in the egg cytoplasm supports the development of such reconstructed embryos to animals that are genetically identical to the animal, which provided the donor cell. However, such cloned animals are often phenotypically abnormal, and exhibit widespread gene dysregulation due to incomplete reprogramming. Thus, it is unclear if cloning, with the current methodology, will ever result in a normal cloned animal.