As far as I've heard, DNA can only be altered prior to birth.
Regardless, "blood ties" are not the same as DNA. No matter your DNA, your birth parents are who they are - and your biologic parents are who they are.
There is such a thing as gene replacement. You can change DNA. Does that mean you can even change who you're blood related to? That would be stupid. You're flesh and blood is what makes you..you (physically).