9.Cell-Cycle+and+Cell+Division(2007)

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1、Chapter9Cell-CycleandCellDivisionOverviewofthecellcycleRegulationofthecellcycleCelldivisionCell-CycleandCellDivision根据增殖状况，细胞分类三类·连续分裂细胞(cyclingcell)·休眠细胞(Go细胞)·终末分化细胞G0期细胞和终末分化细胞的界限有时难以划分，有的细胞过去认为属于终末分化细胞，目前可能被认为是G0期细胞。OverviewofthecellcyclecellgrowthDNAreplicationdi

2、stributionoftheduplicatedchromosomescelldivisionThecellcyclecanbedividedintotwomajorphasesbasedoncellularactivities,interphaseandMphase.Mphaseincludesmitosisandcytokinesis.InterphaseistheintervalbetweendivisionsisdividedintoG1,SandG2phases.sothecellcycleincludesfourph

3、ases:G1,S,G2andMphases.Analysisofalargevarietyofcellshasrevealedgreatvariabilityinthelengthsoftheircellcycle.Thefourstagesofcellcycle,G1isthemostvariable.WhilethetotaltimeofS,G2andMphasesisrelativelyfixed.Itisthecell-cyclecontrolsystemthatensurescorrectprogressionthro

4、ughthecellcyclebyregulatingthecell-cyclemachinery.Theprogressionofcellsthroughthedivisioncycleisregulatedbyextracellularsignalsfromtheenvironmentandinternalsignals.CellcyclecontrolCellCycleCheckpointsCyclinsProgressionregulatoryofcellcycleRegulationofThecellcycleAmajo

5、rcellcycleregulatorypointinmanytypesofcellsoccurslateinG1andcontrolsprogressionfromG1toS.Inadditiontoservingasadecisionpointformonitoringextracellularsignals,STARTisthepointatwhichcellgrowthiscoordinatedwithDNAreplicationandcelldivision.Theproliferationofmostanimalcel

6、lsissimilarlyregulatedintheG1phaseofthecellcycle.Inparticular,adecisionpointinlateG1,calledtherestrictionpointinanimalcells.Theproliferationofthesecellsistriggeredbyplatelet-derivedgrowthfactor,whichisreleasedfrombloodplateletsduringclottingandsignalstheproliferationo

7、ffibroblasts（纤维原细胞）inthevicinityoftheinjuredtissue.CellCycleCheckpointsInmostcells,thecoordinationbetweendifferentphasesofthecellcycleisdependentonasystemofcheckpointsandfeedbackcontrolsthatprevententryintothenextphaseofthecellcycleuntiltheeventsoftheprecedingphasehav

8、ebeencompleted.Atleast,therearethreemajorcheckpointsexistwithinthecellcycle,G1/Scheckpoint,G2/McheckpointandMcheckpoint.TheG