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Lecture 35 Normal Cell Cycle Ozgur Unal
NIS - BIOLOGY Lecture 35 Normal Cell Cycle Ozgur Unal
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Traffic Lights Why are there traffic lights on heavy intersections?
How would the traffic flow without the traffic lights?
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Normal Cell Cycle Traffic light regulates the flow of traffic.
Similarly, in a cell, the cell cycle is regulated. The cell cycle in eukaryotic cells is driven by a combination of two substances that signal the cellular reproduction processes: Cyclins and Cyclin-dependent kinases (CDKs) Cyclins are proteins. Cyclins bind to enzymes called CDKs.
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Normal Cell Cycle Cyclins/CDKs start the various activities that take place in the cell cycle during interphase and mitosis. Different Cyclin/CDK combinations control different activities at different stages of the cell cycle. Example: In G1, the combination of Cyclin with CDK signals the start of the cell cycle. The same cyclin/CDK combination also signals the end of the cell cycle.
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Normal Cell Cycle The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong. Example: A checkpoint near the end of the G1 stage monitors for DNA damage and can stop the cycle before entering the S stage of interphase. There are also other checkpoints. Check out Figure 9.11
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