f gr is a member of the protein kinase oncogene family and was found to have the highest homology to yes gene among the members of the family. Using a v-yes probe, a molecular clone of human c-f gr locus was isolated from a genomic library. Nucleotide sequence determination revealed that the actin gene-like sequence found in v-f gr gene was absent at the corresponding position of the c-f gr gene. Thus, the v-f gr gene product is considered to be a tri-chimeric gene product consisting of viral gag gene and two distinct cellular genes, actin gene and the proto-f gr gene.