The patterning of many developing tissues is orchestrated by gradients of morphogens through a variety of elaborate regulatory interactions.Such interactions are thought to make gradients robust–i.e.resistant to change in the face of genetic or environmental perturbations.Just how this might be done is a major unanswered question.Past numerical simulations and analytical studies suggest that robustness of signaling gradients cannot be attained by negative feedback(of the Hills function type)on signaling receptors but can be achieved through morphogen degradation by non-signaling receptor molecules(or non-receptors for short)such as heparan sulfate proteoglycans.However,empirical evidence of feedback regulating signaling gradients has been reported in the literature.The present paper undertakes a different approach to the role of feedback in robust signaling gradients(and therewith robust biological developments).The overall goal of the project is to investigate the effectiveness of feedback on ligand synthesis,receptor-mediated degradation,non-receptor synthesis and other regulatory processes in morphogen gradient systems.As a first step,we present in this talk a proof of concept examination of a new approach to feedback processes that would lead to robust development.The research is supported in part by NIH Grants R01GM067247,and P50-GM076516.The R01 was awarded through the Joint NSF/NIGMS Initiative to Support Research in the Area of Mathematical Biology.