"Gene sharing" means that the different functions of a protein may share the same gene--that is, a protein produced by a gene evolved to fulfill a specialized function for one biological role may also perform alternate functions for other biological roles.

In the 1980s and early 1990s, Joram Piatigorsky and colleagues coined the term "gene sharing" to describe the use of multifunctional proteins as crystallins in the eye lens. In Gene Sharing and Evolution Piatigorsky explores the generality and implications of gene sharing throughout evolution and argues that most if not all...