Final answer:
Ras protein mutations that inhibit GTPase activity result in the protein being perpetually active. This constant activation of the MAPK kinase pathway leads to unregulated cellular proliferation, contributing to cancer development.
Step-by-step explanation:
The product of a mutant form of Ras that cannot hydrolyze GTP is independent of Receptor Tyrosine Kinase (RTK) activation. In its normal function, the Ras protein acts as a molecular switch cycling between active (GTP-bound) and inactive (GDP-bound) states, controlled by its intrinsic GTPase activity. When mutations impair the GTPase function, Ras remains in the permanently active GTP-bound state, failing to hydrolyze GTP into GDP. This leads to constant activation of downstream signaling, such as the MAPK kinase pathway, regardless of extracellular signals. As a result, the cell undergoes unregulated proliferation, which is a hallmark of cancerous growth.