DNA probes for individual gene products of both the endocrine pancreas (insulin and potentially glucagon) and the exocrine pancreas (several digestive enzymes including amylase) have been prepared by reverse transcription of mRNA and subsequent cloning in E. coli X1776. We propose to utilize the cloned structural gene sequences to probe the organization and expression of the endocrine and exocrine specific genes. The cloned sequences will be used to isolate (by cloning in E. coli X1776) insulin and amylase gene sequences from rat nuclear DNA. The isolaed genes will permit the study of the sequence organization of the structural genes and their contiguous DNA regions. The cloned structural genes will also be used to study changes in their expression during embryonic development as well as alteration in expression accompanying pathogenic states.