One of the most important discoveries from the rise of genomics is that animals, despite their staggering differences in shape and size, utilize a common set of genes. How does the incredible diversity of animal forms arise if animals all contain the same core genetic code? There is a growing body of evidence that changes in the time, location, and amount of gene expression is responsible for the evolution of structures. This project is aimed at determining how regulation of gene expression may have influenced the defining feature of limbs, which is the presence of the hand. Fish do not possess hands, but they possess all of the genes necessary to build one. Thus, the goal of this project is to identify the gene regulatory elements in zebrafish that drive gene expression in fins, and compare them to their counterparts in mouse. This knowledge will help us understand what aspects of fish fin development are ancient, and what aspects have evolved to be specific for building a hand. As the hand is a ?new? feature of limbs that is not present in fins, this project will shed light on how novel features may originate during the evolutionary process. Investigating how genetic switches have influenced the fin to limb transition may provide a general model for how complex and unique features of animals have arisen. In addition, this project is collaboration with a lab in Seville, Spain. This type of collaboration between institutions is beneficial to the greater scientific community by promoting exchange of ideas and techniques in genetics, especially as genomics gets further integrated into evolutionary biology.