clones

Clones are organisms or cells that share identical genetic material. In biology, cloning describes methods that produce genetically identical copies of a target, ranging from simple cells to entire organisms.

Natural cloning occurs in many species. Some organisms reproduce asexually, producing clones without fertilization, such as plants via cuttings or runners, or bacteria by binary fission. Identical twins are natural clones of each other, arising when a single fertilized egg splits into two embryos. Some colonies, such as certain plants or colonial animals, can form large clonal lineages where many individuals share the same genome.

Artificial cloning covers several distinct techniques. Molecular cloning refers to creating copies of DNA fragments, typically using bacterial or yeast hosts and plasmid vectors for research and biotechnology. Reproductive cloning aims to generate a whole animal that is genetically identical to a donor, usually through somatic cell nuclear transfer, where the donor nucleus is inserted into an enucleated egg and developed to an embryo. Therapeutic cloning seeks to produce embryonic stem cells that match a donor’s genetic makeup for potential medical applications, without creating a clone of the whole organism.

Historical milestones include the cloning of Dolly the sheep in 1996, the first mammal cloned from an adult somatic cell. Cloning remains technically challenging and raises ethical, legal, and ecological questions, including concerns about safety, biodiversity, and the implications of human cloning. Proponents point to advances in medicine, agriculture, and conservation, while critics caution against unintended consequences and social implications.