There is a very interesting article in the 'Economist' for this month that covers this topic, and basically we have reached the stage where we can manufacture not only existing beings, but even new forms of life that that have never previously existed. It talked about the potential dangers of this, and how terrorist could use this sort of advanced technology to create malicious beings that could also breed, and the possibilities of new viruses etc, I recommend you guys read if you get the opportunity.