Gurdon transplanted the nucleus of a tadpole intestinal cell into an enucleated frog egg. In this way, he created tadpoles that were genetically identical to the one from which the intestinal cell was taken.
This experiment showed that, despite previous failures, nuclei from somatic cells in a fully developed animal could be used for cloning. Importantly, it suggested that cells retain all of their genetic material even as they divide and differentiate (although some wondered if the donor DNA came from a stem cell, which can differentiate into multiple types of cells).
Robert Briggs and Thomas King
Briggs and King transferred the nucleus from an early tadpole embryo into an enucleated frog egg (a frog egg from which the nucleus had been removed). The resulting cell developed into a tadpole.
The scientists created many normal tadpole clones using nuclei from early embryos. But just like Spemann’s salamander experiments, cloning was less successful with donor nuclei from more advanced embryos: the few tadpole clones that did survive grew abnormally.
Most importantly, this experiment showed that nuclear transfer was a viable cloning technique. It also reinforced two earlier observations. First, the nucleus directs cell growth and, ultimately, an organism’s development. Second, embryonic cells early in development are better for cloning than cells at later stages.