Review Questions

1. What parameters mainly determine the size of an animal or one of its organs?
2. Is a human bigger than a mouse largely because it has bigger cells or more cells, or does cell size and cell number contribute about equally?
3. Why does life depend as much on cell growth (cell enlargement) as it does on cell division?
4. What is a cell-size checkpoint in the cell cycle?
5. How do IGF1 and GGF differ in their effects on rat Schwann cells?
6. GGF but not IGF1 greatly increases the amount of the G1 cyclins (cyclin D1 and cyclin D2) in rat Schwann cells. Does this make sense, given the different effects that GGF and IGF1 have on these cells?