Dolly was a first cloned sheep, derived from a cell of adult sheep. The nucleus of the adult female sheep's cell was transferred to a developing egg cell of another female sheep, from which nucleus was removed. Then, resulting cell was implanted in another sheep (surrogate mother) at blastula stage.
This cell was developed as Dolly and showed that the genes present in differentiated somatic cell of an adult are still capable to revert to an undifferentiated embryonic totipotent state that gives rise to a complete muticellular organism.
Thus, the correct answer to be filled in the blank is 'totipotent.'