if dna can be extracted from skin, hair, bodily fluids, saliva ect...why not blood? if anything, you would think it is our "blood" that contains our dna profiles...rig ht? aparently it doesn't...did you know this? i didn't..i've always wondered what happens when you donate blood... will your genes get mixed? 
Blood has no nucleus, which contains DNA. In the process of maturing, the erythrocyte expels their nucleus containing DNA to make room for carrying oxygen. Hence, blood is typed ABO. If your type is A, and the donor is also A, then the blood is compatible and you can recieve same typed blood 98% of the time. There are other differences in 1 to 2% in Rh factors, and allotypes, which when you recieve blood must be carefully determined, or else, you can get an adverse reaction from the transfusion.