1. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 12 The Cell Cycle

2. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

3. Cell Division in Organisms Unicellular organisms Multicellular organisms – Development from a fertilized cell – Growth – Repair

4. LE 12-2 Reproduction 100 µm Tissue renewal Growth and development 20 µm200 µm

5. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 12.1: Cell division results in genetically identical daughter cells Daughter Cells – duplicate their genetic material – genome – chromosomes

6. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotic Cell Classification Somatic (nonreproductive) Gametes (reproductive cells: sperm and eggs) Chromatin

7. LE 12-3 25 µm

8. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Chromosome duplication (including DNA synthesis) 0.5 µm Centromere Sister chromatids Separation of sister chromatids CentromeresSister chromatids Distribution of Chromosomes During Cell Division Duplicated chromosomes have 2 sister chromatids Centromere

9. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Eukaryotic cell division consists of: – Mitosis – Cytokinesis Meiosis produces gametes

10. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Phases of the Cell Cycle The cell cycle consists of – Mitotic (M) phase – Interphase Interphase subphases: – G 1 phase (“first gap”) – S phase (“synthesis”) – G 2 phase (“second gap”)

11. LE 12-5 G1G1 G2G2 S (DNA synthesis) INTERPHASE Cytokinesis MITOTIC (M) PHASE Mitosis

12. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mitosis is conventionally divided into five phases: – Prophase – Prometaphase – Metaphase – Anaphase – Telophase

13. LE 12-6ca G 2 OF INTERPHASE PROPHASEPROMETAPHASE

14. LE 12-6da METAPHASEANAPHASE TELOPHASE AND CYTOKINESIS 10 µm

15. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Video: Animal Mitosis Video: Animal Mitosis Video: Sea Urchin (time lapse) Video: Sea Urchin (time lapse) Animation: Mitosis (All Phases) Animation: Mitosis (All Phases) Animation: Mitosis Overview Animation: Mitosis Overview Animation: Late Interphase Animation: Late Interphase Animation: Prophase Animation: Prophase Animation: Prometaphase Animation: Prometaphase Animation: Metaphase Animation: Metaphase Animation: Anaphase Animation: Anaphase Animation: Telophase Animation: Telophase

16. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Mitotic Spindle: A Closer Look Mitotic spindle – Microtubules Centrosome, the microtubule organizing center – Two Centrosomes

17. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Aster - extends from each centrosome Kinetochores

18. LE 12-7 Microtubules Chromosomes Sister chromatids Aster Centrosome Metaphase plate Kineto- chores Kinetochore microtubules 0.5 µm Overlapping nonkinetochore microtubules 1 µm Centrosome

19. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Microtubules shorten by depolymerizing Chromosome movement Microtubule Motor protein Chromosome Kinetochore Tubulin subunits

20. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Nonkinetochore microtubules

21. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cytokinesis: A Closer Look Cytokinesis – Animals cleavage, forming a cleavage furrow – Plants cell plate forms Animation: Cytokinesis Animation: Cytokinesis

22. LE 12-9a Cleavage furrow 100 µm Contractile ring of microfilaments Daughter cells Cleavage of an animal cell (SEM)

23. LE 12-9b 1 µm Daughter cells Cell plate formation in a plant cell (TEM) New cell wall Cell plate Wall of parent cell Vesicles forming cell plate

24. LE 12-10 Nucleus Cell plate Chromosomes Nucleolus Chromatin condensing 10 µm Prophase. The chromatin is condensing. The nucleolus is beginning to disappear. Although not yet visible in the micrograph, the mitotic spindle is starting to form. Prometaphase. We now see discrete chromosomes; each consists of two identical sister chromatids. Later in prometaphase, the nuclear envelope will fragment. Metaphase. The spindle is complete, and the chromosomes, attached to microtubules at their kinetochores, are all at the metaphase plate. Anaphase. The chromatids of each chromosome have separated, and the daughter chromosomes are moving to the ends of the cell as their kinetochore micro- tubules shorten. Telophase. Daughter nuclei are forming. Meanwhile, cytokinesis has started: The cell plate, which will divide the cytoplasm in two, is growing toward the perimeter of the parent cell.

25. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Binary Fission Origin of Replication Origin of replication

26. LE 12-11_1 Origin of replication Cell wall Plasma membrane Bacterial chromosome E. coli cell Two copies of origin

27. LE 12-11_2 Origin of replication Cell wall Plasma membrane Bacterial chromosome E. coli cell Two copies of origin Origin

28. LE 12-11_3 Origin of replication Cell wall Plasma membrane Bacterial chromosome E. coli cell Two copies of origin Origin Two daughter cells result.

29. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Bacterial chromosome Chromosomes Microtubules Prokaryotes Dinoflagellates Intact nuclear envelope Kinetochore microtubules Kinetochore microtubules Intact nuclear envelope Diatoms Centrosome Most eukaryotes Fragments of nuclear envelope The Evolution of Mitosis Since prokaryotes evolved before eukaryotes, mitosis probably evolved from binary fission Intermediate types:

30. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 12.3: The cell cycle is regulated by a molecular control system The cell cycle appears to be driven by specific chemical signals present in the cytoplasm Experiment 1 Experiment 2 S S S G1G1 G1G1 M M M

31. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings G 1 checkpoint G1G1 S M M checkpoint G 2 checkpoint G2G2 Control system The Cell Cycle Control System Has specific checkpoints where the cell cycle stops until a go-ahead signal is received

32. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings G1G1 G 1 checkpoint G1G1 G0G0 If a cell receives a go-ahead signal at the G 1 checkpoint, it will usually complete the cycle. G 0 phase

33. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Cell Cycle Clock: Cyclins and Cyclin-Dependent Kinases Two types of regulatory proteins are involved in cell cycle control: – Cyclins – Cyclin-dependent kinases (Cdks)

34. LE 12-16a MPF activity G1G1 G2G2 S MS M G2G2 G1G1 M Cyclin Time Fluctuation of MPF activity and cyclin concentration during the cell cycle Relative concentration

35. LE 12-16b Degraded cyclin G 2 checkpoint S M G2G2 G1G1 Cdk Cyclin is degraded MPF Cyclin Cdk Molecular mechanisms that help regulate the cell cycle accumulation Cyclin

36. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Stop and Go Signs: Internal and External Signals at the Checkpoints Internal signal – kinetochores not attached to spindle microtubules send a molecular signal that delays anaphase External signals – growth factors platelet-derived growth factor (PDGF) human fibroblast cells

37. LE 12-17 Petri plate Scalpels Without PDGF With PDGF Without PDGF With PDGF 10 mm

38. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings External signals – density-dependent inhibition Anchorage dependence – seen in animal cells

39. LE 12-18a Cells anchor to dish surface and divide (anchorage dependence). When cells have formed a complete single layer, they stop dividing (density-dependent inhibition). If some cells are scraped away, the remaining cells divide to fill the gap and then stop (density-dependent inhibition). 25 µm Normal mammalian cells

40. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Cancer cells exhibit neither density-dependent inhibition nor anchorage dependence Cancer cells do not exhibit anchorage dependence or density-dependent inhibition. Cancer cells 25 µm

41. Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Loss of Cell Cycle Controls in Cancer Cells Tumors – Benign tumor – Malignant tumors metastasize Cancer cell Blood vessel Lymph vessel Tumor Glandular tissue Metastatic tumor