Answer all please

Your friend is studying mouse fur color and has isolated the GPCR responsible for determining its color, as well as the extracellular signal that activates the receptor. She finds that, on addition of the signal to pigment cells (cells that produce the pigment determining fur color), cAMP levels rise in the cell. She starts a biotech company, and the company isolates more components of the signaling pathway responsible for fur color. Using transgenic mouse technology, the company genetically engineers mice that are defective in various proteins involved in determining fur color. The company obtains the following results. Normal mice have beige (very light brown) fur color. Mice lacking the extracellular signal have white fur. Mice lacking the GPCR have white fur. Mice lacking cAMP phosphodiesterase have dark brown fur. Your friend has also made mice that are defective in the alpha subunit of the G protein in this signaling pathway. The defective alpha subunit works normally except that, once it binds GTP, it cannot hydrolyze GTP to GDP. What color do you predict that the fur of these mice will be? Why? A certain mutation in the receptor for epidermal growth factor (EGF) causes the mutated receptor protein to send a positive signal along the associated intracellular signaling pathway even when the EGF ligand is not bound to it. This signal leads to abnormal cell proliferation in the absence of growth factor. On the basis of this information, would you class the gene for the EGF receptor as a tumor suppressor gene or a potential oncogene? Explain your answer.