Information AboutCell Cycle |
| CATEGORIES ABOUT CELL CYCLE | |
| cell cycle | |
| cellular processescell cycle | |
| cellular processes | |
| cell biology | |
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The cell cycle is regulated by Cyclin s and Cyclin-dependent Kinase s. Leland H. Hartwell , R. Timothy Hunt , and Paul M. Nurse won the 2001 Nobel Prize In Physiology Or Medicine for their discovery of these central molecules in the regulation of the cell cycle. PHASES The phases of the cell cycle are:
Interphase- usually 90% of the cycle and can divide into subphases:
A surveillance system, so-called " Checkpoints ", monitor the cell for DNA damage and failure to perform critical processes. Checkpoints can block progression through the phases of the cell cycle if certain conditions are not met. For instance, there is a checkpoint which monitors DNA Replication and keeps cells from proceeding to Mitosis before DNA replication is completed. Similarly, the Spindle Checkpoint blocks the transition from Metaphase to Anaphase within Mitosis if not all Chromosomes are attached to the Mitotic Spindle . If this system senses a problem, a network of Signaling Molecule s instructs the cell to stop dividing. They can let the cell know whether to repair the damage or initiate Programmed Cell Death , a form of which is called Apoptosis . Programmed cell death ensures that the damaged cell is not further propagated. For example, a certain protein, called P53 , acts to accept signals provoked by DNA damage. It responds by stimulating the production of inhibitory proteins that then halt the DNA replication process. Without proper p53 function, DNA damage can accumulate unchecked. A direct consequence is that the damaged gene progresses into a cancerous state. Today, defects in p53 are associated with a variety of Cancer s, including some Breast and Colon Cancer s. Some cells, such as Neurons , never divide once they become locked in a G0 Phase . However, recent data has shown that neurons undergoing cell death re-enter the cell cycle. Addition of cell cycle inhibitors prevent this apoptosis. EXTERNAL LINKS
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