What are cell cycle checkpoints? Where in the cell cycle are the checkpoints found (note—incude S phase checkpoint? How do they differ? How are Rb, p53, and MPF involved in cell cycle checkpoints? What events could lead to cell cycle arrest?

In the experiment below, you have treated cells with different cancer drugs, stained them with propidium iodide, and analyzed them by flow cytometry. Which of the following histograms illustrates what you would expect to see in the event that the spindle assembly checkpoint is activated (focus on the solid line, the dotted line is normal cell cycle control)?       1. D 2. C 3. A 4.B

Which of the following need to be expressed to get past the G1 checkpoint and why? Select one: a. All the answers are correct and needed to progress the cell past the G1 checkpoint by expressing the enzymes necessary for DNA replication. Once these proteins are all expressed, the cell has moved past G1 into S phase. b. Primase because this enzyme is needed for DNA replication moving the cell from G1 to S. c. Cyclins because the accumulation of specific cyclins will turn on CDKs needed to turn on gene expression for proteins involved in DNA replication, moving the cell from G1 to S. d. DNA helicase because this protein is needed for DNA replication (part of S phase). So expression will help progress the cell from G1 to S.