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Chapter 12 – The Cell Cycle

Chapter 12 – The Cell Cycle. Cell Division: Key Roles. Genome: cell’s genetic information Somatic (body cells) cells Gametes (reproductive cells): sperm and egg cells Chromosomes: DNA molecules Diploid (2n): 2 sets of chromosomes (humans = 46)

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Chapter 12 – The Cell Cycle

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  1. Chapter 12 – The Cell Cycle

  2. Cell Division: Key Roles • Genome: cell’s genetic information • Somatic (body cells) cells • Gametes (reproductive cells): sperm and egg cells • Chromosomes: DNA molecules • Diploid (2n): 2 sets of chromosomes (humans = 46) • Haploid (1n): 1 set of chromosomes (humans = 23) • Chromatin: DNA-protein complex • Sister chromatids: replicated strands of a chromosome • Centromere: narrowing “waist” of sister chromatids • Mitosis: nuclear division • Cytokinesis: cytoplasm division • Meiosis: gamete cell division

  3. The Cell Cycle • Interphase (90% of cycle) • G1 phase - growth • S phase - synthesis of DNA • G2 phase - preparation for cell division • Mitotic phase • Mitosis - nuclear division • Cytokinesis – cytoplasm division

  4. Late Interphase (G2)

  5. Mitosis

  6. Mitosis

  7. Mitosis • Prophase • Prometaphase • Metaphase • Anaphase • Telophase • ..\ppt lectures cd\animations\12_06AnimalMitosis_VT.swf

  8. Animal Mitosis Overview

  9. Prophase • Chromosomes visible • Nucleoli disappear • Sister chromatids • Mitotic spindle forms • Centrosomes move

  10. Prophase

  11. Prometaphase • Nuclear membrane fragments • Spindle interaction with chromosomes • Kinetochore develops

  12. Mitotic Spindle • Centrosome – organizes the cells microtubules (also called microtubule organizing center) • Aster – radial array of microtubules extends from each centrosome • Kinetochore – on sister chromatids near centromere, have attachment points for microtubules called kinetochore microtubules • Spindle positions chromosomes on metaphase plate

  13. Prometaphase

  14. Metaphase • Centrosomes at opposite poles • Centromeres are aligned • Kinetochores of sister chromatids attached to microtubules (spindle)

  15. Metaphase

  16. Anaphase • Paired centromeres separate; sister chromatids liberated • Chromosomes move to opposite poles • Each pole now has a complete set of chromosomes

  17. Anaphase

  18. Chromosome Movement • How do chromosomes move towards the poles? • Kinetochore fibers shorten at chromosome • Are broken down and removed as tubulin subunits

  19. Telophase • Daughter nuclei form • Nuclear envelopes arise • Chromatin becomes less coiled • Two new nuclei complete mitosis

  20. Telophase

  21. Cytokinesis • Cytoplasmic division • Animals: cleavage furrow • Plants: cell plate

  22. Cytokinesis

  23. Binary Fission • Cell division in a prokaryote • Much simpler than mitosis because prokaryotes lack a nucleus and only have 1 chromosome

  24. Cell Cycle Regulation • Cell cycle control system – a series of checkpoints with go ahead and stop signals (usually a stop sign that needs to be overridden by a go-ahead signal) • Checkpoints at G1, G2, and M • At G1 checkpoint could be directed into G0 phase – most cells in G0, but many can be “called back” into the cell cycle, others cannot (nerve, muscle)

  25. Cancer • When cells lose control of their cell cycle • These cells divide excessively and invade other tissues, potentially shutting them down • Metastasis – the spread of cancer cells to locations distant from their origin

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