Perturbing the expression level of a specific gene in vivo provides a powerful approach towards explaining its function during embryonic development. One technique used for perturbing the level of expression of a specific gene is the application of gene-specific antisense oligodeoxyribonucleotides (ODNs). ODNs are a quick, affordable, and effective means to “knock down” the expression of a gene in order to learn more of its function in vivo. It is a particularly useful tool to study the function of a gene in a specific target tissue, as it acts in a spatially (i.e., site of injection) and temporally (i.e., time of treatment) restricted manner.