The experimental organism first used to demonstrate genomic equivalence was:
Demonstration of genomic equivalence required model where nuclear transplantation technically feasible and embryonic development externally observable. Frogs, particularly Rana pipiens and Xenopus laevis, provided large eggs, simple husbandry, and robust embryonic development ex utero. Their eggs tolerated micromanipulation and enucleation, permitting Briggs, King, and later Gurdon to inject somatic nuclei. Mouse, sheep, guinea pig eggs are small, require implantation, and were not amenable until later mammalian cloning advances. Thus amphibian system pioneered equivalence evidence before exte
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 3: Frog as model for equivalence.
