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Nuclear Transplantation Experiment

In the nuclear transplantation experiment, nuclei from a frog blastula, skin cell or gut epithelial cell were transferred to an unfertilized egg without a nucleus. The nucleus was removed via: irradiation (UV exposure) that destroyed the nucleic information within the unfertilized egg; or surgical excision. Very rarely, the fertilized egg with the transferred nucleus would develop into a mature tadpole.

Similarly, the cloned sheep Dolly was created by injecting an enucleated oocyte with the nucleus of a cell scraped from an udder. These engineered oocytes were implanted into hundreds of surrogate mothers, similarly revealing the totipotency (can give rise to whole individual) of adult mammalian nuclei. As a side-note, in a revealing look at the role of nurture (as opposed to nature) Dolly looked different than the nucleus donor.

EnucleationExposing ova to UV radiation enucleates them by destroying genetic material.
TransplantTransplant nuclei from a frog blastula into an enucleated ovum.
ObserveUpon fertilization, the ovum develops normally despite the transplanted nucleus.
TransplantTransplant nuclei from a differentiated cell (dermal, epithelial, etc) into enucleated ovum.
ObserveThe ovum can still give rise to an embryo regardless of the nucleic donor's tissue type.
ConclusionEnucleation and nucleic transplantation almost always kills the ovum, but the rare cases of survival still show that the nucleus is the agent responsible for blastomere totipotency.
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