Final answer:
In the Ras protein, point mutations can impair the GTPase activity, resulting in the protein being constitutively active and leading to unregulated cell proliferation. This gain of function mutation promotes continuous activation of the MAPK pathway, contributing to cancer development.
Step-by-step explanation:
The parts of the Ras protein affected by point mutations are those involved in its GTPase activity. In normal cell function, the Ras protein cycles between an active and inactive state, by binding and hydrolyzing GTP to GDP. Mutations that impair the GTPase activity of Ras lead to a scenario where Ras is locked in an active form because it can no longer hydrolyze GTP to GDP, effectively leading to continuous signal transduction.
This constitutive activation of Ras results in the continuous activation of the MAPK (Mitogen-Activated Protein Kinase) signaling pathway. The MAPK pathway is responsible for cell proliferation and differentiation. Hence, the mutation in Ras results in uncontrolled cell division, which is a hallmark of cancer. In the context of cancer, a point mutation in the Ras protein that impairs its GTPase activity thus leads to unregulated phosphorylation cascade, promoting gain of function in the entire pathway which can be oncogenic.