41 - MCB 142 Professor Georjana Barnes 11/30/07 Lecture 41...

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MCB 142 Professor Georjana Barnes 11/30/07 Lecture 41 ASUC Lecture Notes Online (formerly Black Lightning) is the only authorized note-taking service at UC Berkeley. Please do not share, copy or illegally distribute these notes. Our non-profit, student-run program depends on your individual subscription for its continued existence. These notes are copyrighted by the University of California and are for your personal use only. Sharing or copying these notes is illegal and could end note taking for this course REVIEW So what I want to do today is continue our progress through understanding cell cycle and how understanding cell cycle will help us understand cancer. This is where we left off last time. Remember we looked at how there was a convergence in understanding the cell cycle of eukaryotic cells based on the experiments done in yeast cells and how in yeast, they were able to identify a number of cell cycle genes. Human geneticists were then able to clone the human counterparts of these genes by looking for those that rescued the yeast mutant phenotype. Here’s a table of a bunch of the genes that are involved in the cell cycle in some way. There are kinases and regulators of kinases and they’re called CDKs and cyclins. They play a big part in the cell cycle as they set the state of the cell cycle, that is, whether the phase is S or M, entry into S or M, or what have you. That’s where we’re starting today, but let’s go back a minute to discuss this Figure 19.5. This figure is misleading. One of your classmates asked me this question after lecture and the reason she was confused is that this figure does not show you a snapshot image of when the experiment started and when the experiment ended. So the figure is trying to beat home the point that in this double mutant analysis, genes act early in the cell cycle and mutants from those genes are epistatic to mutants of genes that act later in the cell cycle. Their phenotypes will show up in a double mutant. But the important point is, if you’re following, you want to say, “As I look at this cell, how does it end up looking like that?” If this is not troubling to you, that’s fine, but the point is, this cell (budding) here is not the same as this cell (non- budding) here. If it were, then this cell would arrest like that. It’s not a snapshot image of the cells at the beginning and end of the cell cycle. It’s a sense of a proof of principle of the epistasis experiment because it shows you what your hypothesis is questioning: does cdc7 act later? Question: If it’s two cell cycles later, can’t the cell divide later? Answer: No, that’s the point. The cell absolutely cannot divide. It stops. If this budding cell finds itself in the cell cycle before the cdc7 step, then you shift to the non-permissive temperature and there’s no cdc7 and you’re stuck. You’ll just arrest where cdc7 normally arrests you. If this cell was after cdc7, then yes, absolutely it would divide. So you can set up this experiment to get this
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This note was uploaded on 04/04/2008 for the course MCB 142 taught by Professor Slatkin during the Fall '08 term at University of California, Berkeley.

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41 - MCB 142 Professor Georjana Barnes 11/30/07 Lecture 41...

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