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CELL CYCLE IRAWAN YUSUF Department of Physiology Faculty of Medicine Hasanuddin University

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  • CELL CYCLEIRAWAN YUSUFDepartment of Physiology Faculty of MedicineHasanuddin University

  • CELL CYCLESThe repeating sequence of growth and division through which cells pass each generation The purpose of the cell cycle is to allow cells to reproduce without alteration of genetic materialThe stages are well preserved between species

  • Why Do Cells Divide?GrowthDevelopmentMaintenanceReproduction

  • Events of Cell CycleG1 Phase -Period of growth; for many organisms this occupies a major portion of the cells life spanS Phase DNA replicates, resulting in duplicate chromosomeG2 Phase Cell prepares for division (mitosis), building necessary materials; centriole and other organelles doubleM Phase Cell division, consisting of nuclear division and cytoplasmic division (cytokinesis)

  • Cell Cycle ProgressionHighly regulated process controlled by a large number of factors include:Growth stimulating factorsGrowth inhibiting factorsEnzymes that alter functional state of other proteins by adding (kinases) or removing (phosphatases) phosphate groupsFailure in the mechanisms by which the cell cycle is regulated can lead to uncontrolled cell growth and the development of cancer

  • The Cell Cycle ControlThere are important checkpoints during the cell cycle:at the G1 S transitionat the S G2 transitionat the G2 M transitionRegulation of the cell cycle occurs as a consequence of cyclin Cdk interactionOther proteins such as P53, Rb and oncogene play a role in regulating the cell cycleP27 : can block entry into S (synthesis) phase.

  • Cell Cycle Is Regulated By Opposing Effects of Positive and Negative FactorsSG2G1MCyclinCdkP53Rb+-

  • Cell Cycle Is Regulated By Opposing Effects of Positive and Negative FactorsTumor Suppressor(P53, Rb)Oncogene(BCl2,BRCA1)Tumor Suppressor(P53, Rb)Oncogene(BCl2,BRCA1)NORMALCANCERCell proliferationCell proliferationCell deathCell death

  • Cyclins and Cyclin Dependent Kinases (Cdk)CyclinCdkProcess regulatedCyclin DCyclin ECyclin ACyclin ACyclin BCdk 4,6Cdk 2Cdk 2Cdk 1(Cdc2)Cdk 1G1 phase progressionG1 to S phaseS phase progressionS through G2M phase

  • Waves of Cyclin-Cdk Activity Control The Cell CycleG1SG1G2MCyclin D-Cdk 4/6Cyclin E-Cdk 2CyclinA-Cdk1Cyclin B-Cdk1GFKinase ActivityTime

  • CHECKPOINTSThe cell cycle control system has checkpoints during G1, G2, S and MCheckpoint signals report cells status:Is the cell big enough?Is environment favorable?Is DNA replicated?Are chromosomes attached to opposite poles?

  • G1G2SprophasemetaphaseanaphaseCytokinesisMitosis