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Friday, November 24, 2017

Modeling Checkpoints in the Cell Cycle




I am always trying to find ways to make the concepts we talk about in AP Bio come to life (no pun intended), especially during the first 6 units which deal primarily with molecular biology. In class, we were working on the cell cycle, focusing on the three checkpoints and the cell regulating itself so the process of making more cells doesn't go awry. Late one night an idea popped into my head, so as my husband was trying to go to sleep, I was busy scribbling notes for a new activity on a post-it note (as seen in the picture below).



 I was thinking about all the cyclin production for the checkpoints and it reminded me of the competitions I've seen in some reality TV shows. On several occasions, a team has to fill some container with water/oil/sand before they can move onto the next part of the competition. It made me think of cyclin reaching a critical level before the cell moves onto the next part of the cell cycle. 




I had had enough of water messes with the labs I've done with my physical science class this year, so I couldn't bring myself to do a race that included sloshing water. Then I remembered that my classroom has inherited an unusually large number of cotton balls, so many that I'm fairly certain we can do the respirometer lab for another 100 years without needing any more cotton balls. As a result, cotton balls represented cyclin. I put together cards for each job in our cell cycle model. It begins with organelle drawing to represent the G1 phase of Interphase as the cell is growing/maturing. At the same time the first cyclin producer is adding "cyclin" cotton balls to a bucket to represent the buildup of cyclin in the cell. Once enough organelles were present and the cyclin had reached a critical level (up to a piece of tape on a bucket), the cell could move onto the next part of the cell cycle. Here the DNA was synthesized. We just had two pop-bead chromosomes that had to be replicated exactly. While the DNA was copied, a second cyclin producer was working on filling the bucket to the critical level. 



If both the DNA replication completed correctly and the 2nd cyclin reached the critical level, the cell would move onto M phase through anaphase. Again, once the critical cyclin level was reached, the cell moved on, completing M phase and going though cytokinesis. And the process could continue. Also during this process, there was a cell cycle checker to make sure the cell was going through the cycle correctly and would halt cyclin production and therefore the cell cycle if anything went wrong. They could then send the cell into G0, its non-dividing state.

The link to the job cards is here.

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