The development of such techniques as transgenesis, saturation mutagenesis, and the polymerase chain reaction (PCR), all of which are described in detail elsewhere in this volume, has revolutionized experimental embryology. However, no single procedure has been more broadly applied across the field than that ofin situhybridization to RNA. This allowed researchers to determine rapidly the spatial and temporal expression of their gene of interest without having to resort to more tedious and less certain approaches requiring the production of antisera against its protein product. As such,in situhybridization has become the standard first step toward the characterization of the developmental significance of a newly identified gene. Of course,in situhybridization tells you nothing regarding translation of the mRNA into protein or about protein’s subsequent localization, modification, or stability. However,in situhybridization remains an extremely powerful tool in enabling the researcher to predict likely developmental functions for gene products rapidly.
