Artificial embryo splitting or embryo twinning , a technique that creates monozygotic twins from a single embryo, is not considered in the same fashion as other methods of cloning. During that procedure, a donor embryo is split in two distinct embryos, that can then be transferred via embryo transfer . It is optimally performed at the 6- to 8-cell stage, where it can be used as an expansion of IVF to increase the number of available embryos.  If both embryos are successful, it gives rise to monozygotic (identical) twins .
The treatment for Leukemia, a cancer in which the bone marrow overproduces white blood cells, could be revolutionized. Today, one of the more successful treatments involves the destruction of a patient’s bone marrow through chemotherapy and the transplantation of healthy marrow cells taken from a closely matched donor. The problem is that many leukemia patients die because they can’t find appropriate donors. With cloning, healthy marrow cells that are perfect genetic matches for patients could be created from the patient’s own cells. Doctors could take a skin cell nucleus and implant it in an enucleated human egg, resetting the cell’s DNA. Once reset, the cell could become an embryonic stem (ES) cell. After the ES cells begin to divide, they could be treated with hormones that would cause them to develop into marrow cells, which could then be returned to the patients. Dame Anne McLaren, head of the Wellcome Institute of Cancer and Developmental Biology at Cambridge, says that if successful, the technique could be extended to other patients suffering from rare disorders where currently bone marrow transplants offer the only hope of a cure.