Shepherd University 1 article published in JoVE Developmental Biology Functional Cloning Using a Xenopus Oocyte Expression System Carol Zygar Plautz1, Hannah C. Williams1, Robert M. Grainger2 1Department of Biology, Shepherd University, 2Department of Biology, University of Virginia We describe a Xenopus oocyte and animal cap system for the expression cloning of genes capable of inducing a response in competent ectoderm, and discuss techniques for the subsequent analysis of such genes. This system is useful in the functional identification of a wide range of gene products.