Final answer:
The gene responsible for increasing the rate of cell division or returning the cell from G0 to the cell cycle during tumor development is an oncogene. It originates as a proto-oncogene, which promotes normal cell growth, becomes an oncogene due to mutations or overexpression, and leads to uncontrolled cell division.
Step-by-step explanation:
In tumor development, the gene that increases the rate of cell division or returns the cell from G0 to the cell cycle is referred to as an oncogene. Originally, such a gene is typically a proto-oncogene, which plays a vital role in normal cell growth and division. However, when a proto-oncogene mutates or experiences overexpression, it becomes an oncogene, leading to the increase in the rate of cell cycle progression and potentially contributing to the formation of a tumor. In contrast, tumor suppressor genes act as the cell cycle's brakes by sending signals to stop the division if abnormalities are detected, essentially acting as a safeguard against uncontrolled proliferation that can lead to cancer.
Thus, the answer is: In tumor development, the oncogene increases the rate of cell division or returns the cell from G0 to the cell cycle. It should be noted that both oncogenes and tumor suppressor genes are essential for proper cell cycle regulation, and their dysregulation can contribute to the development of cancer.