Name: _____________________________________________ Date: _____________ Period #: ____________
Cell Cycle Checkpoints
For cells to progress through the cell cycle they must have
checkpoints. Checkpoints are pauses in the cell cycle to ensure the
cell has no defects and is prepared to divide. Two important
checkpoints are the G1 and G2 checkpoints. If you were to follow a
cell though the cell cycle, from the beginning to the end, the first
checkpoint the cell has to pass is the G1 checkpoint. In order for the
cell to move from the G1 to the S phase, two conditions must be
satisfied: 1) the environment has to be favorable for division and 2)
all of the DNA must be intact. If these conditions are met, the cell
will commit to the S phase and begin DNA synthesis. If either one of
these conditions are not satisfied, the cell will enter a resting state
called the G0.
The second major checkpoint is really important because it
prevents cells with damaged DNA from entering mitosis. In order
to the cell to pass the G2 checkpoint, 2 conditions must be satisfied:
1) all of the DNA must be replicated and 2) all of the DNA must be
intact. If these conditions are satisfied, the cell will commit to the M
phase and divide. If there is damage to the DNA or if there were
mistakes made during DNA replication, the cell will use specialized
machinery to attempt to repair the damage. If the damaged is
repaired, the cell can move to the M phase and divide. If the
damage can be fixed, the cell will undergo apoptosis (programmed
cell death) and commit cell suicide.
To review your knowledge of the cell cycle you will need to visit the
Nobelprize.org. You may be asked to do this activity independently or at
home. Go to the following link:
http://nobelprize.org/educational/medicine/2001/index.html
Click and follow the directions to Control the Cell Cycle and play the
Control the Cell Cycle Game; be sure to finish out the program by
watching the short video clip.
Name: _____________________________________________ Date: _____________ Period #: ____________
Answer the following questions from this handout on the back. You
may need to refer to your notes on mitosis to answer the questions
correctly.
1. What types of checkpoint are involved in the cell cycle?
2. How did this activity reinforce the concepts associated with
mitosis and cell division?
3. Name 3 circumstances where normal mitosis is used by an
organism.
4. Why is it important for cancer researchers to understand mitosis
5. Mutations in DNA that alter the reregulation of the cell cycle
control can lead to cancer. What kinds of alterations to cell cycle
regulation could result in cancer.
6. If you were going to develop a drug to stop cancer from
developing, what stage of the cell cycle target? Why?