Divide and destroy: an overview of poisonous divisionals

A patent application can in effect destroy itself. It works like this: a priority filing might claim a kinase which has an acceptable homology with a particular sequence listing—call that kinase-SL. The filing which is eventually made claims the kinase as originally claimed and a more general description of it, such as any kinase which has general binding characteristics for a class of proteins, of which kinase-SL is a member—call that the class of kinases.