Blood is a popular way for courts to find criminals because of the DNA. One problem though: Don't blood cells shed their nucleus when they mature? I know there's got to be something else going on because if it weren't they wouldn't use blood as a primary DNA source, but what is it that's going on?

I think they grab large immune cells such as phagocytes and such. These can be sperated rther easily in a centrifuge and I think they would use some of the other components of blood. In order to get a karyotype done on a fetus they grab the ambiotic fluid around the fetus and they cenrtifuge that. This is an early process for genetic screening.

Only mature red blood cells lose their nucleus; the various types of white blood cells (neutrophils, monocytes, eosinophils, lymphocytes, etc) keep their nucleus for their entire life and are high enough in number to have enough DNA to ID a person as psynapse said...