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Reproductive cloning |
Artificial twining | Therapeutic cloning | ||
Somatic cell nuclear transfer | Embryonic cell nuclear transfer | |||
What is created? | An adult organism | An adult organism | An adult organism | A blastocyst (early embryo) which has its stem cells harvested |
Is it human? | No – this would be illegal. | This would be illegal in the UK unless it was to produce an embryo with three parents to prevent mitochondrial disease. | No – this would be illegal. Some people think it should be allowed in special circumstances | Yes, but it is strictly regulated. The cells can be human (a human nucleus and egg), non-human or hybrid (a human nucleus and non-human egg). |
What is it a clone of? | The genetic parent which donated the nucleus. | The early embryo nucleus-donor. The donor embryo isn't developed into an adult, so the only living organism with identical genetic material is another clone of the embryo generated at the same time (if one was created). | Its twin. | The genetic parent which donated the nucleus – usually a patient. |
What method is used? | SCNT. Genetic engineering can be carried out at the same time. | Embryonic cell nuclear transfer. Genetic engineering can be carried out at the same time. | Embryo splitting. Genetic engineering can't be easily carried out at the same time. | SCNT. Genetic engineering can be carried out at the same time. |
Since when? | 1962 – Gurdon transferred a frog intestinal cell nucleus to a frog egg, which developed into a tadpole. | 1952 – Briggs and King transferred a frog embryo nucleus to an enucleated frog egg, which developed into a tadpole. | 1891 – Hans Driesch split a sea urchin embryo which developed into two sea urchins. | Therapeutic cloning of mouse somatic cells achieved in 2000, and of human somatic cells in 2013. |
What are the clones used for? | To improve breeding stock in farm animals. To increase numbers of endangered animals and try to revive extinct species. Transgenic clones can create medical products for humans. | Their creation tests the possibilities and allows researchers to refine techniques and methods for SCNT. Enables women with faulty mitochondria to produce children free from the disease. | To improve breeding stock in farm animals. | The stem cells produced can be used to study genetic diseases, test treatments and create tissues (and organs?) for transplant. |
Advantages | Can clone an animal with known traits. | Genetic material requires relatively little reprogramming. | Can be seen as ethically less wrong because it mimics a natural process. Techniques used are relatively simple. | There is no risk of immune rejection if the cells are re-implanted in patients. Can be seen as ethically less wrong because the potential benefits outweigh the negative aspects. |
Disadvantages | Problems with reprogramming of genetic material. Problems once the embryo is transferred into a surrogate mother. | Problems once the embryo is transferred into a surrogate mother. | Some problems once the embryo is transferred into a surrogate mother. | Problems with reprogramming of genetic material. |