Content Warning: This section of the guide includes discussion of eugenics and ableism.

Cloning is a process that produces two organisms with identical genes. Organism cloning is complex and typically uses a process called somatic cell nuclear transfer, or SCNT, in which the nucleus of an adult somatic cell is transferred into an egg cell whose nucleus has been removed. Provided the egg cell starts to divide normally and form a zygote, it is then implanted in a uterus and allowed to develop into a fetus. The resulting offspring is a clone of the original, though not an exact duplicate, as the nucleus of the adult somatic cell may have mutations in its DNA. The mitochondrial DNA from the donor egg cell is also unique. Cloning can also be achieved using embryo splitting, resulting in monozygotic (identical) twins. This process is not thought to produce true clones.

Dolly the sheep was the first mammal to be successfully cloned using SCNT in 1996. It took 435 attempts before scientists were able to produce a successful embryo. Since then, many different animals have been successfully cloned, including horses, dogs, cats, and monkeys. Concerns surrounding cloning typically include the fear that it will one day be practiced on humans.