[
Neuron,
1998]
The question of how genes contribute to normal individual differences in behavior has captured our imagination for more than a century. Several fundamental questions come to mind. How do genes and their proteins act in the nervous system and in response to the environment in order to cause individual differences in behavior? Do genetic differences between natural variants arise from alterations in the structural or regulatory region of a gene? Can we predict which genes for behavior, identified by mutant analysis in the laboratory, will have natural allelic variation? Three groundbreaking studies (Osborne et al., 1997; Sawyer et al., 1997; de Bono and Bargmann, 1998) published in the past year demonstrate that we now have the knowledge and technological capability to address these questions empirically. Each study has successfully identified a single major gene for a given behavior and, with the aid of transgenic animals, shown that its gene product is responsible for naturally occurring individual differences