Final answer:
An oncogene is a mutated form of a proto-oncogene that causes cells to divide uncontrollably, potentially leading to cancer. The overactive oncogene can ignore cell cycle checkpoints, similar to a car with a stuck accelerator. This unregulated growth is a primary factor in the development of various cancers.
Step-by-step explanation:
An oncogene is a mutated version of a proto-oncogene, which is a gene that normally helps to control cell division. Oncogenes can arise from these normal genes when a mutation occurs, causing the once-normal proto-oncogene to promote uncontrolled cell growth and division. This usually happens when the mutated gene becomes overactive like a car accelerator being stuck at full throttle, continuously signaling for cell division even when it is not needed. An example of an oncogene is myc, which when overexpressed can lead to cancers such as Burkett's Lymphoma.
Proto-oncogenes are considered as positive cell-cycle regulators that help manage the cell cycle. However, when a proto-oncogene is altered, it can override cell cycle checkpoints, leading to an increase in the rate of cell-cycle progression. This is how oncogenes contribute to the development of cancer by allowing cells to proliferate uncontrollably.
Unlike oncogenes, tumor suppressor genes normally act as brakes on cell division. When these genes are mutated, they fail to stop the cell cycle, similarly contributing to cancer development.