DNA Database - Put simply, bad idea
Just in case anyone thinks a fully inclusive DNA database of the entire nation and any visitors to the nation is a good idea, I offer you this thought:
Millions and millions of records on a database are subject to two huge compromising problems. First being that they require many administrators to keep up to date. Secondly, the bigger the amount of data stored the larger risk/amount of clerical error.
Now, if you were leading a criminal organisation, and heard news of this development you're going to want access to that information aren't you. So you'll get a man on the job either creating the thing of administrating it.
This government has a history of sending confidential information in the post and losing it, leaving it on trains or having it on display for the press to photograph. As for trusting clerical accuracy; watch the news on expenses roll in. Jack Straw's council tax bill anyone?
If you trust this government to keep hold of that kind of information visit your GP. It's likely they'll need to pass you on to a neurologist.