Oncogenes are Mutant Forms of Proto-Oncogenes

Oncogenes arise from the mutation of proto-oncogenes. Since they are mutant forms of proto-oncogenes, oncogenes resemble proto-oncogenes in that they code for the production of proteins involved in growth control. However, oncogenes code for an altered version (or excessive quantities) of these growth-control proteins, thereby disrupting a cell's growth-signaling pathway.