They could accomplish the same thing with entierly different forms of nucleic acics that are not D.N.A, we could have a more effective dog with something other than D.N.A, and they would still be unable to reproduce with other animals. If animals and organisms already can't reproduce with different versions of the same form of D.N.A, theres no way they could with entirely different forms of D.N.A or other nucleic acids.