Cancer and cell cycle control:
The cell cycle, or cell-division cycle, is the series of events that takes place in a cell leading to its division and duplication (replication). In cells without a nucleus (prokaryotic), the cell cycle occurs via a process termed binary fission. In cells with a nucleus (eukaryotes), the cell cycle can be divided in two brief periods: interphase—during which the cell grows, accumulating nutrients needed for mitosis and duplicating its DNA—and the mitosis (M) phase, during which the cell splits itself into two distinct cells, often called "daughter cells". The cell-division cycle is a vital process by which a single-celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells, and some internal organs are renewed. Key molecules within the cancer cell cycle control system: CDKs CDKs - cyclin dependent kinases. The activity of CDKs rises and falls as the cell progresses through the cycle. Oscillation leads to cyclical changes in the phosphorylation of proteins that regulate major events in the cell cycle. DNA replication, mitosis, chromosome condensation etc. Key molecules (2): Cyclins
Cyclines are CDK regulators. Unless tightly bound to a cyclin CDKs have no protein kinase activity. Cycles of synthesis and degradation hence the name. CDK levels remain constant. Cyclical changes in cyclin levels result in cyclic assembly and activation of the cyclin-CDK complexes. This activation triggers cell-cycle events. Cellcyclecontrol/ inhibitors: Two families of genes, the cip/kip family and the INK4a/ARF (Inhibitor of Kinase 4/Alternative Reading Frame) prevent the progression of the cell cycle. Because these genes are instrumental in prevention of tumor formation, they are known as tumor suppressors. The cip/kip family includes the genes p21, p27 and p57. They halt cell cycle in G1 phase, by binding to, and inactivating, cyclin-CDK complexes. p21 is activated by p53 (which, in turn, is...
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