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The Cell Cycle: Cell Growth, Cell Division

The Cell Cycle: Cell Growth, Cell Division. Where it all began…. You started as a cell smaller than a period at the end of a sentence…. And now look at you…. How did you get from there to here?. Why do cells divide?. Reproduction asexual reproduction one-celled organisms

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The Cell Cycle: Cell Growth, Cell Division

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  1. The Cell Cycle: Cell Growth, Cell Division

  2. Where it all began… You started as a cell smaller than a period at the end of a sentence…

  3. And now look at you… How did you get from there to here?

  4. Why do cells divide? • Reproduction • asexual reproduction • one-celled organisms • Growth and Development • from fertilized egg to multi-celled organism • Repair and Replacement • replace cells that die from normal wear & tear or from injury amoeba

  5. Cell Cycle

  6. Cell cycle • Cell has a “life cycle” cell is formed from a mitotic division cell grows & matures to divide again cell grows & matures to never divide again G1, S, G2, M liver cells G1G0 epithelial cells,blood cells, stem cells brain / nerve cells muscle cells

  7. Interphase • 90% of cell life cycle • cell doing its “everyday job” • produce RNA, synthesize proteins/enzymes • prepares for duplication if triggered I’m working here! Time to divide& multiply!

  8. G0 signal to divide Interphase • Divided into 3 phases: • G1= 1stGap • cell doing its “everyday job” • cell grows • S= DNA Synthesis • copies chromosomes • G2 = 2ndGap • prepares for division • cell grows (more) • produces organelles,proteins, membranes

  9. green = key features Interphase • Longest phase of the cell cycle • Consists of G1, S, G2 • Cell prepares for mitosis • replicates chromosome • DNA & proteins • produces proteins & organelles

  10. ACTGGTCAGGCAATGTC Organizing DNA DNA • DNA is organized in Nucleosomes • double helix DNA molecule • wrapped around Histones • like thread on spools • DNA-protein complex =Chromatin • organized into long thin fiber • condensed further during mitosis histones chromatin double stranded chromosome duplicated mitotic chromosome

  11. Copying DNA & packaging it… • After DNA duplication, chromatin condenses • coiling & folding to make a smaller package mitotic chromosome DNA chromatin

  12. double-strandedmitotic humanchromosomes

  13. homologous chromosomes homologous chromosomes sister chromatids Mitotic Chromosome • Duplicated chromosome • 2 chromatids • narrow at centromere • contain identical copies of original DNA single-stranded homologous = “same information” double-stranded

  14. Mitosis • Dividing cell’s DNA between 2 daughter nuclei • “dance of the chromosomes” • 4 phases • Prophase • Metaphase • Anaphase • Telophase

  15. Mitosis

  16. I.P.M.A.T. Overview of mitosis interphase prophase (pro-metaphase) cytokinesis metaphase anaphase telophase

  17. green = key features Prophase • Chromatin condenses • Becomes chromosomes • chromatids • Centrioles move to opposite poles of cell • animal cell • Protein fibers cross cell to form mitotic spindle • microtubules • actin, myosin • coordinates movement of chromosomes • Nucleolus disappears

  18. green = key features Transition to Metaphase • Prometaphase • Special proteins attach to the centromeres • creating kinetochores • microtubules attach at kinetochores • connect centromeres to centrioles • Nuclear envelope fragments

  19. green = key features Anaphase • Sister chromatids separate • move to opposite poles • pulled at centromeres • pulled by motor proteins “walking”along microtubules • actin, myosin • increased production of ATP by mitochondria • Poles move farther apart • polar microtubules lengthen

  20. green = key features Telophase • Chromosomes arrive at opposite poles • Nuclear envelop starts to reappear • nucleoli form • Chromosomes uncoil • no longer visible under light microscope • Spindle fibers disperse • Cytokinesis • cell division

  21. Cytokinesis • Animals • constriction belt of actin microfilaments around equator of cell • cleavage furrow forms • splits cell in two • like tightening a draw string

  22. Mitosis in whitefish blastula

  23. Cytokinesis in Plants • Plants • Cell Plate • vesicles line up at equator • derived from Golgi • vesicles fuse to form 2 cell membranes • new cell wall laid down between membranes • new cell wall fuses with existing cell wall

  24. Cytokinesis in plant cell

  25. onion root tip

  26. G1/S checkpoint • G1/S checkpoint is most critical • primary decision point • “Go Ahead signal” • if cell receives “GO” signal, it divides • internal signals: cell growth (size), cell nutrition • external signals: “growth factors” • if cell does not receive signal, it exits cycle & switches to G0 phase • non-dividing, working state

  27. Cell cycle signals inactivated Cdk • Cell cycle controls • Cyclin • regulatory proteins • levels cycle in the cell • CDK • cyclin-dependent kinases • phosphorylates cellular proteins • activates or inactivates proteins • MPF • triggers passage through different stages of cell cycle activated Cdk

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