The behaving brain of a fly

The use of Drosophila as a suitable system to answer behavioural questions is usually based on the availability of mutant phenotypes. Indeed, the 'single-gene' approach to behaviour was a very illuminating strategy in practical and conceptual terms, and served to prove that the genetic mechanisms sustaining behaviour could be analysed. However, the essence of neurogenetics goes for beyond the utilitarian use of mutants as tools to dissect behavior. Our main contention is that the study of the genetic basis of behaviour requires the study of genomes, rather than single genes, and their functional organization. Here, we use two aspects of behaviour, olfaction and movement control, as examples to illustrate the intricate, albeit understandable, relationship between the genome and behaviour. At present, these examples offer only a glimpse into this relationship. Further progress might be reached if studies on the regulation of functionally related genes are undertaken. On these grounds, it appears that the answer to many fundamental questions about behaviour that are amendable to experimentation might come from the work on Drosophila, providing that the required multidisciplinary efforts are focused on this organism.