The heritability represents the sum of genetic variances contributed by all genes and their interactions, and a substantial H2 is a prerequisite for gene mapping studies as well as artificial selection [ 2]. Because both the genetic background and the environmental rearing conditions can be controlled precisely, Drosophila melanogaster presents an attractive model system for investigating the genetic architecture of behavior. Flies display a wide repertoire of behaviors, many of which occur across the animal kingdom (e.g. aggression [ 3• and 4], courtship and
mating [ 5, 6 and 7], sleep [ 8 and 9], learning and memory find more [ 10]). Evolutionary conservation of fundamental molecular mechanisms and cellular pathways allows us to uncover general principles that apply across behavioral phenotypes and across phyla. Studies aimed at the genetic dissection of behaviors in Drosophila have utilized both mutational analyses of individual genes and quantitative genetic approaches. The former approach relies on a change in the behavior as a consequence of disruption of a specific gene, whereas the latter correlates variation in the behavioral phenotype among individuals with genotypic differences to identify simultaneously multiple genes that contribute to the behavioral phenotype. Furthermore, systems genetics approaches in which DNA sequence PD-0332991 solubility dmso variants are correlated
with variation in transcript abundance levels and variation in organismal phenotype have demonstrated that behaviors are dynamic phenotypic manifestations that emerge from transcriptional networks of pleiotropic genes [11•• and 12].
Both environmental effects and epistatic interactions [13••, 14, 15, 16, 17•• and 18] modulate emergent behavioral Etofibrate phenotypes. In addition, epigenetic regulation may contribute to long-term behavioral modifications [19]. This entire genetic system is further influenced by the development of the organism and is a culmination of its evolutionary history while at the same time providing targets for future evolutionary adaptation (Figure 1). Both single gene studies and systems genetics approaches, and a combination of these strategies, have contributed to our understanding of the genetic underpinnings of behaviors. Classically, identification of genes that contribute to Drosophila behaviors has relied on chemical or P-element insertional mutagenesis. Unlike studies on development, which focus on events that happen pre-eclosion, studies on behavior generally require the survival of viable and functional adults. Thus, hypomorphic rather than null mutants are typically used for the study of behaviors. Early mutagenesis screens identified genes that, when disrupted, give rise to large behavioral effects. For example, period mutations have dramatic effects on circadian rhythm [ 20] and the paralytic mutation results in unambiguous locomotion deficits [ 21].