Professor Harlow explains that over the years, we have learned that the cell cycle can easily be divided in a couple of major decision points or action points where cells specifically do a series of necessary tasks.

Ed Harlow, Ph.D. is the Chair of the Department of Biological Chemistry and Molecular Pharmacology at Harvard Medical School. His research focuses on developing new ways to analyze and identify genes involved in key regulatory pathways in the cell. “Over the years, we have learned that the cell cycle can easily be divided in a couple of major decision points or action points where cells specifically do a series of tasks that need to go through. The two major ones that are the replication of the DNA, the actual chromosomes being replicated and duplicated into an exact copy something called DNA synthesis, is highlighted as the S-phase in the eukaryotic cell cycle world. And the other big part is mitosis, when the cell actually divides and that's called M-phase. And those two phases are kind of the big action points in everything big happens in the cell division cycle. However, there are obviously very tightly controlled, you obviously don't want to do these at inappropriate times or without the right type of regulation, so there actually are control points that happen just before the action of DNA synthesis or before M-phase and we call those in our world gap phases or G1 and G2. So it really does look like a cycle when you begin to think about it. It's a circle in which cells go from G1 to S, G2 to M, and back to G1 and they continue this cycle around. And at each point there are relatively complicated decision making points that a cell assesses whether it's a good idea to divide or not or go to the next stage.”

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