Oncogenes are mutant genes from the group of genes that regulate cell growth and division called protooncogenes. Protooncogenes can be found in every normal cell and perform important function. They can be transformed into oncogenes by a point mutation, translocation (in many leukemias and lymphomas) or amplification which is multiplying the number of copies. For example characteristic translocation for chronic myelocytic leukemia is so-called Philadelphia chromosome. That is a mutual translocation between 9 and 22 chromosomes. Oncogenes were first discovered in viruses.