Steen Willadsen

Agricultural Research Council's Institute of Animal Physiology, Cambridge, he successfully used cells from early embryos to clone sheep by nuclear transfer.^[2][3] The procedure he developed was essentially identical to the one used to create Dolly the sheep, although nuclei from a mature sheep were used instead of sheep embryos. Prior to the nuclear transfer experiments, Willadsen had developed methods for freezing sheep and cow embryos,^[4] embryo manipulation methods for producing genetically identical animals (primarily identical twins in sheep, cattle, pigs, and horses),^[5] and for producing mammalian chimaeras, including interspecies chimaeras.^[6]