True about Proto-oncogenes are

Proto-oncogenes are normal cellular genes encoding growth stimulating proteins.Oncogene can be defined as an altered gene whose product acts in a dominant manner to accelerate cell growth or cell division. Oncogenes are generated by "activation" of proto-oncogenesThere are principally four classes of genes, which when mutated to cause gain-, or loss-of-function or inappropriate regulation, can result in the development of a tumour. These are proto-oncogenes, tumour suppressor genes, DNA repair genes, and genes regulating apoptosis or evasion of immune surveillance.Ref: Harper; 30th edition; Pg: 726