Show Details

Bloody Evidence

October 2, 2007

DNA is found inside the nucleus of a cell. But red blood cells have no nucleus, so a listener asks: How do forensic experts extract DNA from blood?


A crime-scene conundrum. I’m Bob Hirshon and this is Science Update.

You’ve seen it on CSI – forensic experts collecting blood samples from the crime scene for DNA analysis. But listener Andrea Bowen of Doncaster, England correctly noted that DNA is found inside the nucleus of cells. But since red blood cells have no nucleus, extracting DNA from them would be impossible. So how do forensic scientists get DNA from blood? We turned to Jack Ballantyne, the associate director for research at the National Center for Forensic Science.

JACK BALLANTYNE (National Center for Forensic Science):
Fortunately for forensic scientists we have white blood cells present in blood to basically help us fight invaders, pathogens and other bad things for the human body. And these white blood cells have nuclei and there are plenty of them in a sample of blood.

If you have a science question, call us at 1-800-why-isit. If we use it on the air, you’ll win a Science Update mug. I’m Bob Hirshon, for AAAS, the science society.