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Chapter 9

Chapter 9 - Cell Cycles.docx

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BIOL 204
Dr.Roland Treu

CHAPTER 9 CELL CYCLES91 The Cycle of Cell Growth and Division An OverviewBefore dividing most cells enter period of growth in which they synthesize proteins lipids and carbs and during mitosismeiosis replicate their nuclear DNA cytokinesis partitioning nuclei to each of 2 daughter cellsSequence of eventscell cycle91aThe Products of Mitosis Are Genetic Duplicates of the Dividing CellDuplication result of1Master program of molecular checks and balances to ensure orderlytimely progression t cell cyclewin cell cycle process of DNA synthesis replicates each DNA chromosome into 2 copies 2w near perfection3Structuralmechanical web of interwoven cables and motors of mitotic cytoskeleton tht separate DNA copies into daughter cellsTime when cells need to be diff from parent cellsmeiosiswhere daughter cell has only half theof chromosomesoAlso genetic traits carried are in diff combo from those of parent cellnoF as gametes in animalsother gameteszygote and as spores in plantsfungi91b Chromosomes Are the Genetic Units Divided by MitosisEach chromosome composed of one linear DNA molecules along w assocd proteins which stabilize DNA assist in packaging DNA during cell division and influence expression of indvd genesMost euks have 2 copies of each type of chromosome in their nuclei and chromo complment said to be diploid or 2noEx Humans have 23 diff pairs of chromosomes for a diploid number of 46 chromosomes 2n46oTF if only one copyhaploid or n of chromosome setsploidy of a cellspeciesReplication of DNA of each indvd chromosome creates 2 idential sister chromatidsoHeld tgh until mitosis separates them into daughter nucleioAar of division each daugher nucleus receives exactly same type of chromosomes containg same genetic info as parent cell entering division oEqual distribution of daughter chromosomes to each of 2 cells tht result from cell divisonchromosome segregationPrecision of replication and segregation creates group of cells called a clone all genetically identical except for rare chance mutations92 The Mitotic Cell CycleInterphasesto1 and longest phaseoCell grows and replicates its DNA in prep for mitosis aka Mphase and cytokinesisInt regulatory ctrls trigger each phase ensuring processes of one phase are completed successfully before next Int mechanisms also regulate overallof cycles cell is allowedoSubject to ext influences caused by other cellsviruses as well as signal mol hormones growth factors death factors92a Interphase Extends from the End of One Mitosis to the Beginning of the Next MitosisInterphase begins as daughter cell from previous division cycle enters initial period of cytoplasmic growthG phase1G phase1oCell makes RNAs proteins and other cellular mol but not nuclear DNA oG stands for gap referring to absence of DNA synthesisoOnly phase tht varies in length for a given species oStage in which many cell types stop dividingG phase which in humans cells of NS enter into 0once fully matureoIf cell going to divide DNA replication begins initiating S phase of the cell SsynthesisS phaseoCell duplicates chromosomal proteins as well as DNA and cont synth of other cellular molG phase2ndo2 gap post DNA synth completion
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