Hmm. I can think of Embryo.
Near the beginning, a scientist runs over a dog and uses an experimental technique to save it. I think he cloned a new dog and grew it to adulthood rapidly, making an exact copy. Later on, he tries it on a gravely injured human woman. The human clone becomes evil. Don't recall her turning into a dog but it's been years since I saw the movie (and it sucked so I didn't pay much attention in the first place).
agree!
One of the more insane films of the 70's.