ABSTRACT
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Amphibians are the animals in which cloning was first achieved in multicellular organisms. The history of cloning up till the present time has been recently reviewed [1]. Briggs and King [2] were the first to produce normal larvae by transplanting nuclei from early embryos into enucleated eggs. Their work suggested that, as cells differentiate, they lose their ability to promote normal development of eggs. However, soon after the work of Briggs and King, experiments with Xenopus showed that even the nuclei of differentiated intestinal cells could elicit the formation of normal adult male and female frogs [3]. This established the principle that cell specialization does not necessarily require any stable loss of genes or genetic activity.
