Final answer:
Oncogenes promote cell proliferation and survival, and when mutated, they can cause cancer. Protooncogenes can become oncogenes, and tumor suppressor genes prevent uncontrolled cell division. Several mutations in both types of genes are required to transform a normal cell into a cancer cell.
Step-by-step explanation:
Oncogenes are a type of gene that promotes cell proliferation and survival. When mutated, they can cause cancer. Protooncogenes are normal genes that, when mutated, become oncogenes. They can encode for growth factors, protein kinases, GTPases, or transcription factors, and their activation can override cell-cycle checkpoints and push a cell forward in its cycle, stimulating cell division. In contrast, tumor suppressor genes send stop signals during a cell cycle and prevent uncontrolled division. Mutations in tumor suppressor genes can lead to unwanted cell division and proliferation. It may take several mutations in both types of genes to transform a normal cell into a cancer cell.