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.
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.