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Joinson Dastari was a highly qualified scientist, especially a bio-geneticist. He was considered a pioneer of genetic engineering by the Sixth Doctor. The Second Doctor once said that he had enough letters after his name for two alphabets.
By 1985, he was Head of Projects on Space Station Camera, where he used technological augmentation to make an Androgum, Chessene of the Franzine Grig, into a genius.
With Chessene, a prototype time machine and an unaltered Androgum, Shockeye of the Quawncing Grig, Dastari abducted the Doctor from the space station. Having landed in the city of Seville on the planet Earth, he worked to find the secret of the Rassilon Imprimatur for the Sontaran Stike. He later supervised the partial genetic transformation of the Doctor into an Androgum.
Dastari walked in on Chessene as she lapped up the blood of another incarnation of the Doctor, who had come to rescue his past self. Faced with this evidence, Dastari was forced to concede what the Doctor had tried to tell him earlier; regardless of her augmented intellect, Chessene was still fundamentally an animal at heart. Although he attempted to free the Doctor and Peri Brown, when Chessene discovered his treachery, she shot and killed him.