Or have you been arrested? Or have you undergone a security clearance investigation in the united states?
I don't think you have to give DNA for a security clearance
Actually, that's not true. There's a new technique called familial searching that can locate relatives that have had their DNA taken. The cops can then ask a brother, sister, parent, or cousin if they have a particular kind of male or female relative.
Most military/contractor DNA is now in a "personnel recovery" database with the government, too.