ABSTRACT
The key to understanding form is development; the process through which a single-cell egg gives rise to a complex, multi-billion-celled animal … I have described the genetic toolkit for development and how its discovery was driven by the study of spectacular mutants that made the wrong number of body parts, or put a part in the wrong place, or lacked some major structure all together. Most of the time, thankfully, nature gets it right and flies and babies are born with the right number of parts in all the right places.
