Description: The purpose of this portion of the application are to 1) construct microarrays containing target DNAs representing the entire genome of Dictyostelium discoideum, 2) to use these arrays to determine expression profiles for wide type Dictyostelium grown under a variety of conditions, and 3) to use expression profiles as a molecular phenotype with which to characterize the potential functions of thousands of genes mutagenized in Project I of this proposal. These data will be used in Project III to cluster phenotypes and lead to testable hypotheses regarding the function of these genes.