Describe the molecular biology behind each situation.

1. describe what would be the effects of deleting the N-terminal signal sequence of the PDGF receptor in an epithelial cell? Please describe both the effects on protein localization and on the cell's ability to regulate its cell cycle.

2. describe A cell has a temperature-sensitive mutation in the Ras GAP. At low temperature the phenotype of the cell is normal. What phenotype would you expect to observe at higher temperature?

3. describe Phosphotidyl inositol is made in the lumen of the smooth endoplasmic reticulum. describe how might a serious mutation in the flippase that normally distributes phosphotidyl inositol disrupt signalling through G-protein coupled receptors?