Genetic investigation of quantitative behavioral traits

Genetic investigation of quantitative behavioral traits Neuropsychiatric geneticists are now focusing considerable attention on the investigation of quantitative human behavioral traits, postulating that such phenotypes could be more straightforward to genetically map than neuropsychiatric disorders. Such syndromes are among the most complex of human traits, a fact that may explain why efforts to elucidate their etiology have been singularly unsuccessful. Although quantitative phenotypes may be simpler than clinically heterogeneous diseases, there is still little evidence that human behavioral quantitative trait loci (QTL) will be easy to identify. For this reason there is a tremendous appeal in using the powerful tools available for genetic investigation of simple model organisms; genes implicated in behavioral variation in flies or worms can then be targeted for various forms of analysis in mammals, including humans. This strategy depends on the identification of suitable measures of behavior in simple systems. Circadian rhythms are a classic example. Investigations of clock mutants in Drosophila led to the discovery of the first circadian rhythm gene, period, and ultimately to cellular pathways underlying circadian behavior [1]; this line of investigation was subsequently successfully extended in rodents as well as humans [2].