I know that the DNA is chemically separated from the cell that contains it and stretched, pulled (not sure what the proper word would be) outward creating a linear sort of pattern that you might be familiar with from movies.
I suppose one could test the DNA in your hair or your skin to be sure that the transfused DNA was not in it.
Not being a biologist I have no idea what happens to transfused blood - i.e. how long it stays in your system, etc.