Therapeutic cloning, or somatic-cell nuclear transfer (SCNT), begins with the same process used to create Dolly, the famous cloned sheep, in 1996. A donor cell from a body tissue such as skin is fused with an unfertilized egg from which the nucleus has been removed. The egg ‘reprograms’ the DNA in the donor cell to an embryonic state and divides until it has reached the early, blastocyst stage. The cells are then harvested and cultured to create a stable cell line that is genetically matched to the donor and that can become almost any cell type in the human body.Many scientists have tried to create human SCNT cell lines; none had succeeded until now. Most infamously, Woo Suk Hwang of Seoul National University in South Korea used hundreds of human eggs to report two successes, in 2004 and 2005. Both turned out to be fabricated. Other researchers made some headway. Mitalipov created SCNT lines in monkeys in 2007. And Dieter Egli, a regenerative medicine specialist at the New York Stem Cell Foundation, successfully produced human SCNT lines, but only when the egg’s nucleus was left in the cell. As a result, the cells had abnormal numbers of chromosomes, limiting their use.

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