And so if there's a mutation that takes place in the Ras gene, and the mutation basically destroys the Gtpa's activity of this g protein, then once the protein is activated, it will remain in the on position. It will remain active. And that means it will continually stimulate these processes. And the signal transduction pathway will continue the process of cell growth, cell division and cell proliferation. So we see that one way by which a signal transduction pathway may malfunction is if a gene encoding for a protein that is part of that pathway is actually mutated. For instance, the rat gene that codes for the Ras protein in the EGF pathway is the most commonly mutated gene that leads to tumor growth of epithelial and epidermal cells.