2 sets of DNA in one blood sample?

Assuming you were transfused with blood with no plasma or white blood cells, then no, you would not have 2 sets of DNA. Blood that is transfused has been seperated ie it has no plasma or white blood cells, just red blood cells. As red blood cells have no nucleus, they have no DNA :)

A blood transfusion does not contain white blood cells. These cells are part of the immune system and if transfused into you they would recognise you as non-self and attack your tissues leading to GVHD.

Blood only contains the plasma (which will contain donor antibodies, but these will be degraded by your white blood cells) and red blood cells. Mature red blood cells have no nucleus (so no DNA) as their primary role is oxygen transport and use all available space to pack in as much haemaglobin as possible. Therefore your blood would only contain your DNA.

They normally do not need blood anymore for DNA anyway. They can just swab the inside of your mouth.

BTW: The only time that someone can have 2 sets of DNA is if there was a parasitic twin (A fraternal twin that died inuteuro) and was absorbed into the body of the surviving twin.

its chimeraism. U have to differnt sets of DNA- ones from ur twin. It is very interesting stuff, google "chimera" and read more about it

If this is true, I doubt that there are a *lot* of people coming up against it. It sounds like an extremely rare freak event.

Short answer, almost certainly not. See link below for more details.

good question! I received loads of blood last year (25 pints of blood plus a load of plasma), so thanks for asking this.