[tsimionescu]

In general, the instructions for creating a copy of an object can be very different from instructions for creating an original from scratch, because instructions for copying can use information already in instance A. And DNA is certainly instructions for copying, not for building from scratch.

How far you'd get using DNA to create some organism from scratch is unclear, but it's certainly not very far at all. You certainly can't create a whole eukaryotic cell just from DNA, even with all put current knowledge of organic chemistry plus our ability to study how current cells actually work (no one has come even slightly close to building a self-replicating prokaryotic cell).

Edit: imagine source code for a compiler that is allowed to strcpy() bits of the currently running compiler. It's a legitimate way to create a running compiler, but it's not what we'd normally consider "source code".