Final answer:
Normal Ras expression regulates cell growth and differentiation, while overexpression or mutation can lead to oncogenic transformation, causing uncontrolled cell division and potentially leading to cancer.
Step-by-step explanation:
Normal Ras expression activates a signal transduction pathway with a sequence of events: Ras protein activates RAF, RAF phosphorylates MEK, which in turn phosphorylates ERK. Once ERK is activated, it enters the nucleus and triggers responses that lead to protein expression, cellular metabolism, and cell division. This is essential for the regulation of cell proliferation and differentiation.
However, when there is Ras overexpression or a mutation that inhibits GTPase activity, Ras can be activated at inappropriate times, leading to uncontrolled cell proliferation. This mutation may cause Ras to become an oncogene, and the inability of Ras to hydrolyze GTP into GDP can result in uncontrolled growth, and ultimately, cancer. In fact, up to 30% of all cancers may be due to abnormal Ras activity. Consequently, understanding Ras regulation and its mutations is crucial in cancer research, where the aim is to develop treatments preventing tumor growth while preserving normal cells.