Their products, the proteins constitute the basic units of neurobiological functions. In the last 15 years, with the advent of recombinant DNA techniques, we have witnessed the discovery of the biochemical diversity of brains. Today more than 10.000 different proteins are thought to act and interact in the brain of an insect and, maybe, some 50.000 in that of a mammal. We must give up all hope to understand a brain by restricting our curiosity to the network level. Genetics has not only revealed this molecular complexity, it also provides the means to exploit it.
Genes are equally important with respect to the old question of homology.
All brains, including our own, serve similar needs. They operate on similar principles and must have the same basic functional organization . However, at the morphological level this similarity is by no means obvious. Generations of biologists have battled about the homology of certain organs, tissues or cells in distantly related species and more often than not have failed to reach an agreement. This is different at the level of the genes.