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The Cell Cycle

The Cell Cycle. Chapter 12. The Key Roles of Cell Division. cell division = reproduction of cells All cells come from pre-exisiting cells Omnis cellula e cellula. Unicellular organisms  division of 1 cell reproduces organism Binary fission. Multicellular organisms. Why cells reproduce

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The Cell Cycle

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  1. The Cell Cycle Chapter 12

  2. The Key Roles of Cell Division • cell division =reproduction of cells • All cells come from pre-exisiting cells Omnis cellula e cellula

  3. Unicellular organisms  division of 1 cell reproduces organism • Binary fission

  4. Multicellular organisms • Why cells reproduce • Development/Growth • Replacement • Repair

  5. 20 µm 100 µm 200 µm (a) Reproduction (b) Growth and development (c) Tissue renewal

  6. Cellular Organization of Genetic Material • chromosome = strand of DNA • 2 sets of 23 chromosomes in humans = 46 • genome = All DNA in a cell 20 µm

  7. chromatincomplex of DNA and protein

  8. Somatic cells= body cells (2 trillion in adult) • two sets of chromosomes (pairs= diploid) • Produced by mitosis - 1 diploid cell  2 identical diploid cells • Gametes sperm and eggs • have 1 set = haploid • Produced by meiosis– 1 diploid cell  4 unique cells • Occurs only in ?

  9. Identical cells Unique cells Diploid Haploid

  10. Concept check • 1. start with a fertilized egg 5 cell divisions produce how an embryo of ______ cells • 2. a chicken has 78 chromosomes in a somatic cell. How many chromosomes in a chicken sperm?

  11. Human Arabidposis

  12. The cell cycle = time from new cell to when it divides Interphase – 90% of time Mitosis4o min INTERPHASE S (DNA synthesis) G1 G2 MITOTIC (M) PHASE

  13. Cell Division • Mitosis = division of the nucleus • Cytokinesis = division of cytoplasm

  14. INTERPHASE • G1 phase – cell grows, gets ready • S phase – DNA replicates • G2 phase – cell grows, gets ready If cycle is 24 hrs, how long each phase? S (DNA synthesis) G1 G2 MITOTIC (M) PHASE

  15. Signs of interphase?

  16. S phase of Interphase • Chromosomes (DNA) replicate • Sister chromatids = 2 • Centromere = constricted region

  17. 0.5 µm Chromosomes DNA molecules Chromosome arm Chromosome duplication (including DNA synthesis) Centromere Sister chromatids Separation of sister chromatids Centromere Sister chromatids

  18. MITOSIS video • Prophase • Prometaphase • Metaphase • Anaphase • Telophase • Cytokinesis by late telophase

  19. I. Prophase • Chromosomes condense • Mitotic spindle forms from centrioles • Nuclear membrane breaks apart

  20. The mitotic spindle (formation begins in prophase) Aster Centrosomes Prophase G2 of Interphase  Aster = radial array of microtubules

  21. Prophase

  22. II. Prometaphase • Spindle microtubules attach to kinetochores of chromosomes • Chromosomes pulled towards center of cell

  23. III. Metaphase • chromosomes (sister chromatids) line up at the metaphase plate • midway between spindle’s two poles

  24. Aster Centrosome Sister chromatids Microtubules Chromosomes Metaphase plate Kineto- chores Centrosome 1 µm Overlapping nonkinetochore microtubules Kinetochore microtubules 0.5 µm

  25. G2 of Interphase Prophase Prometaphase Chromatin (duplicated) Centrosomes (with centriole pairs) Early mitotic spindle Fragments of nuclear envelope Centromere Aster Nonkinetochore microtubules Prometaphase G2 of Interphase Prophase Kinetochore Nuclear envelope Plasma membrane Chromosome, consisting of two sister chromatids Kinetochore microtubule Nucleolus

  26. Telophase and Cytokinesis Metaphase Anaphase Nucleolus forming Metaphase plate Cleavage furrow Metaphase Anaphase Telophase and Cytokinesis Daughter chromosomes Nuclear envelope forming Centrosome at one spindle pole Spindle

  27. IV. Anaphase • sister chromatids separate • microtubules shorten – depolymerize to move chromosomes toward opposite ends of cell

  28. V. Telophase • Identical nuclei form at opposite ends of cell • Chromosomes less condensed

  29. Cytokinesis • Division of cytoplasm • animal cells • cleavage furrow • plant cells • cell plate

  30. 100 µm Cleavage furrow Daughter cells Contractile ring of microfilaments (a) Cleavage of an animal cell (SEM)

  31. Vesicles forming cell plate Wall of parent cell 1 µm Cell plate New cell wall Daughter cells (b) Cell plate formation in a plant cell (TEM)

  32. Nucleus Chromatin condensing Nucleolus 1 Prophase

  33. Chromosomes 2 Prometaphase

  34. 3 Metaphase

  35. 4 Anaphase

  36. 10 µm Cell plate 5 Telophase

  37. Evolution of Mitosis • mitosis is thought to have evolved from binary fission • Some protists exhibit cell division intermediate between binary fission and mitosis

  38. The cell cycle is regulated by a molecular controls • Short length – ex. skin cell • Longer length – ex. Neurons • Specific signal molecules in cytoplasm

  39. G1 checkpoint Control system S G1 G2 M M checkpoint G2 checkpoint

  40. Application: Cancer Mutation in cell cycle genes • Breast cancer cells dividing

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