We propose to study the organization of the multiple major urinary protein genes isolated from a mouse gene library. To aid us in this analysis, we well try to isolate DNA probes which will allow us to distinguish genes coding for the different proteins in the family. Also we will measure the rates of transcription of MUP mRNA in nuclei isolated from livers at various stages of development. We will try to develop a cell free system for transcribing MUP genes in vitro. In addition the size and regulation of nuclear MUP precursor RNAs will be examined. Finally, the cellular distribution of MUP genes will be examined by in situ hybridization.