When Sec was a pure Dalek, he was able to merge with a human (however, it is unknown if he needed to be prepared to be able to do this)
Sec was a genius at genetics.
Sec was ruthless, and would do anything to keep the Daleks alive. After he merged with a human, his mind somewhat changed, and even thought what he had done was wrong. Going so far as to be allies with the Doctor, a sworn enemy of the Daleks.
Doctor Who series 2 (season 28):
Doctor Who series 3 (season 29):