This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure and function of protein, Subject name: Biochemistry
True about Proto-oncogenes are 
Select and explain. 
A. Normally involved in cell cycle proliferation, B. Produces tumor, C. Normally involved in suppression of tumour production, D. True about Proto-oncogens on mutation causes cancer
A: Normally involved in cell cycle proliferation
Answer: A: Normally involved in cell cycle proliferation 
Explanation: 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