Mammalian cloning: From Dolly to embryonic stem cells

Josef Fulka, Jr.

Institute of Animal Production, Prague 10, Czech Republic (


            Since Dolly the sheep was born in 1996 the success in the production of cloned animals has been reported, after transfer of somatic cell nucleus into enucleated oocyte, in ten another mammalian species (mouse, mule, horse, rat, rabbit, cat, cow, goat, pig and interspecies-specific clone: muflon-sheep). However, the success of mammalian cloning is extremely low - approximately 3%, some of cloned animals have serious health and morphological abnormalities and this clearly speaks against the use of this procedure in humans. Nuclear transfer (cloning) does not exclusively lead to production of an embryo from which a new individual will be eventually born (reproductive cloning). More promising is so called „therapeutic cloning“. Also in this case the embryo is produced. This embryo is not transferred into the uterus, but it is used for the production of so called „embryonic stem cells“. It is generally believed that with these cells some presently untreatable diseases and serious injuries could be treated. However, even in this case, some problems and still unanswered questions exit.