The present invention provides a mutant oligonucleotide composition encoding a cellular c-Src tyrosine kinase oncogene. Methods for isolating, expressing and characterizing recombinant Src mutant polypeptide are also provided. The invention further relates to methods for utilizing such oligonucleotides, polypeptides, agonists and antagonists for applications, which relate to research, diagnostics, and clinical arts. More specifically, this invention provides methods of diagnosing, treating, immunizing, and creating transgenic animals based on use of such mutant Src.