Two methods of cloning
Globe and Mail Update
Saturday, August 18, 2001
Embryo splitting, September 1999
- A fertilized egg is taken when the cell division has reached a total of eight cells.
- The cells are split into quadruplet embryos with two cells each. All four embryos, including their DNA, remain true to the original.
- Two quadruplet embryos are transferred into each surrogate mother. Both monkeys become pregnant with only one embryo.
- The first monkey miscarries.
- The second monkey gives birth to Tetra, a genetic copy of the original embryo.
Nuclear transfer technology, February, 1997
Sources: Oregon Regional Primate Research Center and New York Times News Service
- DNA from a mammary cell is removed from an adult sheep.
- An unfertilized egg is removed from another sheep. Its nucleus, containing the DNA, is removed.
- The mammary cell DNA and unfertilized egg are fused.
- The egg develops into an embryo, which is transferred into a surrogate mother.
- The lamb contains DNA from the adult donor, but grows up to have slightly different characteristics.