Final answer:
The gene that signals a cell to grow and divide when activated but remains silent when not is either a proto-oncogene or a tumor suppressor gene. Proto-oncogenes promote growth, while tumor suppressor genes halt it to prevent tumor growth. Mutations can transform these genes into oncogenes that lead to cancer.
Step-by-step explanation:
The type of gene you are referring to, which gives signals for a cell to grow and divide when activated, and remains silent when not, falls into two categories: proto-oncogenes and tumor suppressor genes. Proto-oncogenes are responsible for promoting cell growth and division when they are needed, and include products like cell-surface receptors for growth factors or cell-signaling molecules. On the other hand, tumor suppressor genes send signals to stop the cell cycle when there are potential problems, or to cease division when cells have enough contact with neighboring cells, a function crucial for preventing tumor growth.
However, when these genes undergo mutations or changes in regulation, which could affect gene expression at various levels such as epigenetic or transcriptional changes, they can contribute to the uncontrolled cell growth that characterizes cancer. A well-known example is the RAS gene, which becomes an oncogene when mutated, leading to unregulated growth and potentially cancer.