Hah, yeah, when I was 17 I got done for petty vandalism and had to give a swab of saliva as DNA to see if I might be matched to any previous serious crimes in the area. Of course nothing came up. It's supposed to have been wiped off the record after five years, but come on, this is the government we're talking about here. My DNA will be on their database till the end of time. So yes, I have contributed my DNA, albeit not to the greatest of human pursuits!
Also I'm on the organ donor list. I filled a form and ticked all the boxes. When I die, they're having everything.