Mammalian Cloning A laboratory in Scotland reported the first successful cloning of a mammal in 1996 How did they do it? Nuclear transfer involves transferring the complete genetic material (the DNA contained in a nucleus) from one cell into an unfertilized egg cell whose own nucleus has been removed. Cells are removed from the udder of an adult ewe and cultured. The nucleus is removed from an unfertilized egg The egg is then fused to one of the cultured cells with an electric pulse. After growing for six days the embryo is implanted in a ewe. Normal gestation and birth (embryos tend to be larger than normal). The result was Dolly Limitations Only one out 300 transfers worked fetal cells are better (1/50) imprinting? contamination with fetal cells? need diploid tissue culture cells age effects? only in sheep? works with cows George and Michael first success with mice this summer fifty clones, two generations (clones of clones)! Implications Agriculture best of breed? disease susceptibility bioengineered animals therapeutic proteins in the milk Polly - has human blood factor IX more lean meat George and Michael pig organs for human transplants a cig? Endangered species Humans? a dangerous form of reproduction? bioengineered humans? Or not? Current status Lots of progress in producing bioengineered sheep and cows from embryonic or fetal cells The use of adults has not been replicated adult cloning is not needed for bioengineering, the most profitable use No attempts with humans, yet (that we know of) too dangerous (most embryos fail, some very late) many ethical concerns [ Biol 207 ] [ Bell ] [ CSU Chico ] [ Library ] This document is maintained by: Jeff Bell Last Update: Wednesday, August 12, 1998