Having one of my usual "why is this so" thoughts this morning and was pondering what happens to the DNA from the original donor giving a heart after its transplanted in the body of the receiver.

I know that every cell in a person's body is replaced after something like 12 years (not sure exactly) but I am wondering if those new cells would be based on the DNA of the original transplanted cells or on the DNA of the new "caretaker" of the heart?

Also... how might this also apply to something like a bone marrow transplant? Does the transplanted bone marrow produce blood that contains DNA from the original donor and if so, for how long? How might this affect DNA testing in a murder situation for instance?

Dr Karl... are you out there?