Developmental pathways first elucidated by genetic studies in the fruit fly Drosophila melanogaster are conserved in vertebrates. The hedgehog pathway, first discovered because of its involvement in early Drosophila development, plays a key role in human embryogenesis. Dissruption of this pathway has been associated with congenital anomalies of the central nervous system, axial skeleton, limbs, and occasionally other organs. Many developmental genes continue to play an important role in regulation of cell growth and differentiation after embryogenesis, and mutations that lead to activation of the hedgehog pathway result in skin cancer and other malignancies in children and adults.