The question assumes that there is a difference between invention and discovery. There isn't. Invention is a kind of discovery. The apparent distinction arises from our separation of physical and mental processes. But this is a purely artificial separation, a human conceit, because (unless you're a dualist) mental processes are physical processes. Specifically, mental processes are computational processes, which are…
A fignaft is a small pink bird from the island of slamp. It has a short triangular beak well adapted to plucking seeds out of the hard cones of the humnit bush. It was nearly hunted to extinction by the umaglots, until their chief shaman declared the bird to be a repository of the souls of men lost at sea. Since then it has made a remarkable recovery.
In contrast to the mental process required to invent an imaginary bird such as this, the folks who discovered DNA used tools to image cell internals such that the structure of the contents was revealed.
When DNA was discovered, something about the structure of the external world was made clear to us, and many other processes could be clarified as a result. The fignaft bird, on the other hand, only reveals the contents of my mind, and is constructed entirely of existing knowledge.