Final answer:
Nuclear transplantation experiments have shown that every cell in a multicellular organism contains the same set of genes in its nucleus, which was demonstrated by transplanting nuclei from one cell type into enucleated eggs and observing normal development.
Step-by-step explanation:
The key finding of nuclear transplantation experiments is that every cell in a multicellular organism contains the same set of genes in its nucleus. This was demonstrated by John Gurdon and Shinya Yamanaka in 1962 when they transplanted nuclei from intestinal cells of a frog into enucleated eggs. The eggs developed into normal tadpoles, proving that the genes present in the transplanted nucleus were not lost during development.