BIOL231 Chapter 18 Discussion Questions -Describe what takes place in the three phases of interphase. -What are cell cycle checkpoints? Where are they found in the cell cycle? What do they check for? disdis-How do Rb and p53 negatively regulate the cell cycle in G1? -Describe the events that occur in the initiation and elongation of DNA replication in S phase (Be specific!) -For each phase of mitosis, make sure you can describe the events that take place as well as the mechanism (ie, from where to do microtubules form? How do they attach? What proteins are involved in chromosome condensation? Etc.)