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Name: Tom B.
Status: Educator 
Age: 50s
Location: N/A
Country: N/A
Date: 2002

This was a question from a student in my forensic science course during the summer. If a person gives blood at a blood bank and this blood is given to someone needed a transfusion who later commits a crime, would the DNA of the donor show up on tests of DNA information?

That is a very interesting question! My compliments to your student. Well, first things first: For the record, _mature_ human red blood cells do not have a nucleus, so they do not carry DNA. But of course, there are other cells in the blood that do, such as cells of the immune system, immature blood cells, etc., and I am assuming that whole blood was transfused. That being said, I still am leaning towards saying that yes, it is _possible_ that the transfused blood could show up, since the PCR test is so sensitive.

Of course, the person receiving the transfusion would have to spill some of his or her blood at the crime scene for this to work. If the criminal loses some hairs or skin, which is tested for DNA, that would not show the donor's DNA. Another thing to keep in mind: red blood cells live for about 120 days, after which they are replaced.

Paul Mahoney, Ph.D.

The donated blood has very little nucleated blood cells in it. Any nucleated cells (wbc's) are rapidly lost from circulation after I HIGHLY doubt it.

Peter Faletra Ph.D.
Assistant Director
Science Education
Office of Science
Department of Energy

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