Since the mammalian genome (its entire genetic information) is broadly comparable to those of invertebrate animals, how do we evolve this extra complexity present in vertebrates, compared to some rather rudimentary animals?
This fourth lecture describes some of the mechanisms used to achieve this, such as the complexification of gene structures (alternative splicing), the complexification of gene regulations (pleiotropy and multifunctionality) and the complexification of certain gene regulatory networks and their interrelationships. These various points lead us both to address the concept of "neo-functionalization", a mechanism made possible by gene duplications, and to revisit the notion of "homology", a fundamental and historic notion in this field of evo-devo.
This lecture also begins to emphasize the idea of the existence of internal constraints in the construction of organisms, resulting precisely from the complexification of mechanisms and structures, an old concept but one that today is finding new experimental and theoretical bases.
