Steen Willadsen

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Steen Willadsen
Born 1943
Copenhagen, Denmark
Residence Orlando, United States of America
Alma mater Royal Veterinary College of Copenhagen
Known for The first cloning of a sheep.
Awards Recipient of the Royal Agricultural Society of England's Gold Medal for Research, 1985, and the International Embryo Transfer Society's Pioneer Award, 2005[1]
Scientific career
Fields embryologist

Steen Malte Willadsen (born 1943 in Copenhagen, Denmark) is a scientist credited with being the first to clone a mammal using nuclear transfer.

Willadsen graduated from the Royal Veterinary College of Copenhagen (1969), and received a PhD in reproductive physiology from there (1973). In 1984, at the British 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 the one used a decade later by Wilmut et al. to produce Dolly, the sheep, although in the latter case, nuclei from a mature sheep, i.e. not from sheep embryos, were used. Prior to the nuclear transfer experiments, Willadsen had developed methods for freezing sheep and cow embryos,[4] and 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]


  1. ^ Reproduction, Fertility and Development 2005, 17
  2. ^ Nuclear transplantation in sheep embryos
  3. ^ Willadsen, S.M. (1989): Cloning of sheep and cow embryos. Genome 31, 956 - 962.
  4. ^ Willadsen, S.M. (1977): Factors affecting the survival of sheep embryos during deep-freezing and thawing. in The Freezing of Mammalian Embryos. Ciba Found. Symp. 52,NS., Eds. Elliott and Whelan, Elsevier/ Excpt. Medica/ N.Holland, Amsterdam, 175 - 189.
  5. ^ Willadsen, S.M. (1979): A method for culture of micromanipulated sheep embryos, and its use to produce monozygotic twins. Nature, Lond. 277,298 - 300.
  6. ^ Fehilly, C.B., Willadsen, S.M., and Tucker, E.M. (1984): Inter-specific chimaerism between domestic sheep (Ovis aries)and domestic goat (Capra hircus). Nature, Lond. 307, 634 - 636

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