As the mapping and sequencing portions of the Human Genome Project proceed, determining the actual function of genes becomes of major interest. Dr. Hudson proposes to develop a simple system to measure gene expression in yeast with the goal of creating a resource useful in the determination of gene function. The plan is to synthesize a unique oligonucleotide probe for every yeast gene and array these probes on membranes such that relative gene expression can be determined by hybridization with first strand cDNA. The envisioned system, based on routine hybridization techniques, will be "low tech" and therefore usable by most laboratories. The system will allow individual investigators to determine relative gene expression for different physiological conditions, as well as the effects of specific knockouts/knockins on other genes and pathways. To evaluate the system and begin data collection, yeast cultures will be grown under a number of different conditions of physical and metabolic stress. The relative expression of the genes will be determined for each of these conditions. This information will be made available through the World Wide Web. Other investigators will be encouraged to contribute data to this public database.