The current effort to develop Xenopus tropicalis as a model system for genetic analysis of vertebrate development unites the strengths and versatility of Xenopus laevis with the power of genetic approaches. A key requirement for X. tropicalis genetics is the establishment of genomics resources that will support the mapping and cloning of genes identified by mutation. The goal of this project is to generate a genetic map for Xenopus tropicalis , by identifying polymorphic markers and using them to screen a map cross DNA panel by PCR. By looking for the co-segregation of polymorphic markers with specific mutations, investigators will be able to map genes identified by mutant phenotype, as a first step in positional cloning. This project thus establishes a foundation for the integration of genetic, molecular and mutational analyses in this model system, and it ensures that genetic studies in X. tropicalis will be applicable to studies of molecular mechanisms underlying vertebrate development.