1. Oncogene: Oncogenes are specific base sequences present in the genome of Oncoviruses (e.g. Provirus) that can code for Oncoproteins responsible for production of cancer.
2. Protooncogene: Protooncogenes are the homologous base sequences of oncogenic sequences. They have been discovered from the chromosomal materials of normal animals like Birds, Rodents, Primate and even human beings. They may be converted to true oncogenes by mutation.