Carcinogens are the physical, chemical, or biological agents (like UV rays or tobacco smoke) that trigger the transformation of proto-oncogenes into oncogenes.
Step 1: Normal cells have genes called cellular oncogenes (c-onc) or proto-oncogenes. Step 2: When these genes are activated under certain conditions (like mutations or exposure to carcinogens), they transform into viral oncogenes or active oncogenes. Step 3: These activated oncogenes lead to the uncontrolled cell division characteristic of cancer.