1. The Cell Cycle and Cellular Reproduction

2. Outline  Interphase  Mitotic Stage  Cell Cycle Control  Apoptosis  Mitosis  Mitosis in Animal Cells  Cytokinesis  Cancer  Prokaryotic Cell Division

3.  Most of the cell cycle is spent in interphase.  Interphase has three distinct phases of its own. Interphase

4. G 1 - Cell doubles its organelles and accumulates materials needed for DNA synthesis.G 1 - Cell doubles its organelles and accumulates materials needed for DNA synthesis. S - DNA replication.S - DNA replication. G 2 - Cell synthesizes proteins necessary for cell division.G 2 - Cell synthesizes proteins necessary for cell division.

5. Mitotic Stage  Cell division stage that includes mitosis (nuclear division) and cytokinesis (cytoplasm division).

6. Cell Cycle

7. Cell Cycle Control  Researchers have identified an internal signal protein (cyclin) that increases and decreases as the cell cycle continues.

8.  Cyclin must be present for the cell to proceed from the G 2 stage to the M stage and from G 1 stage to S stage.  Allows time for any damage to be repaired.

9. Cell Cycle Control

10. Apoptosis  Often defined as programmed cell death. Cells routinely harbor enzymes (caspases) necessary for apoptosis to occur.Cells routinely harbor enzymes (caspases) necessary for apoptosis to occur.

11.  Apoptosis is ordinarily held in check by inhibitors, but can be unleashed by internal or external signals.  Mitosis increases and apoptosis decreases the number of somatic cells.

12. Apoptosis

13. Mitosis  When a eukaryotic cell is not undergoing division, the DNA within the nucleus is a tangled mass of chromatin.

14. Chromatin condenses into chromosomes.Chromatin condenses into chromosomes.  Each species has a characteristic number of chromosomes. Diploid (2n) - Two of each kind.Diploid (2n) - Two of each kind. Haploid (1n) - One of each kind.Haploid (1n) - One of each kind.

15. Mitosis  During mitosis, a diploid nucleus divides to produce diploid daughter nuclei. Two identical chromatids are called sister chromatids.Two identical chromatids are called sister chromatids.

16.  Sister chromatids are attached to each other at the centromere. During nuclear division, sister chromatids separate at the centromeres, and each duplicated chromosome gives rise to two daughter chromosomes.During nuclear division, sister chromatids separate at the centromeres, and each duplicated chromosome gives rise to two daughter chromosomes.

17. Duplicated Chromosomes

18. Mitosis in Animal Cells  Each centromere in an animal cell contains a pair of barrel-shaped organelles (centrioles) and an array of short microtubules (aster).

19.  Centromeres organize mitotic spindle, which contains many fibers, each composed of a microtubule bundle.

20. Mitosis in Animal Cells  Prophase Chromatin has condensed.Chromatin has condensed. Nucleolus disappears.Nucleolus disappears. Nuclear envelope disintegrates.Nuclear envelope disintegrates. Spindle begins to assemble.Spindle begins to assemble.

21.  Prometaphase Kinetochores develop on centromere.Kinetochores develop on centromere.  Attach sister chromatids to spindle fibers.

23.  Metaphase Chromosomes, attached to kinetochore fibers, are in alignment at center of cell.Chromosomes, attached to kinetochore fibers, are in alignment at center of cell.

24.  Anaphase Sister chromatids split, producing daughter chromosomes.Sister chromatids split, producing daughter chromosomes.  Daughter chromosomes are pulled to opposite poles.

25.  Telophase Spindle disappears as new nuclear envelopes form around the daughter chromosomes.Spindle disappears as new nuclear envelopes form around the daughter chromosomes.  Chromosomes become diffuse chromatin again.  Nucleolus appears in each daughter nucleus.

27. Plant Cell Division  Meristematic plant tissue retains the ability to divide throughout the plant’s life. Found at root and shoot tips.Found at root and shoot tips.

28. Phases of Mitosis in Plant Cells

29. Cytokinesis  Cytokinesis accompanies mitosis in MOST cells. Mitosis without cytokinesis results in a multinucleated cell.  Begins in anaphase, continues in telophase, but does not reach completion until interphase begins.

30. Cytokinesis  Animal Cells Cleavage furrow, membrane indentation between daughter nuclei, begins as anaphase nears completion.Cleavage furrow, membrane indentation between daughter nuclei, begins as anaphase nears completion.

31.  The cleavage furrow deepens when a band of actin filaments (contractile ring) forms a circular constriction between the two daughter cells.

32. Cytokinesis in Animal Cells

33. Cytokinesis  Plant Cells Rigid cell wall surrounding plant cells does not permit cytokinesis by furrowing.Rigid cell wall surrounding plant cells does not permit cytokinesis by furrowing.

34.  Cytokinesis begins with formation of a cell plate which eventually becomes new plasma membrane between the daughter cells.

35. Cytokinesis in Plant Cells

36. The Cell Cycle and Cancer  Cancer is a growth disorder that results from the mutation of genes regulating the cell cycle. Carcinogenesis, development of cancer, tends to be gradual.Carcinogenesis, development of cancer, tends to be gradual.

37. Characteristics of Cancer Cells  Lack differentiation.  Have abnormal nuclei.  Form tumors. Loss of contact inhibition.Loss of contact inhibition.

38.  Undergo metastasis. New tumors distant from primary tumor.New tumors distant from primary tumor.  Undergo angiogenesis. Formation of new blood vessels.Formation of new blood vessels.

40. Origin of Cancer  Mutations in DNA repair mechanisms.  Mutations to proto- oncogenes and tumor- suppressor genes. Proto-oncogenes become oncogenes.Proto-oncogenes become oncogenes.

41.  Telomerase allows cancer cells to continually divide.

42. Prokaryotic Cell Division  Asexual Reproduction - offspring are genetically identical to the parent.

43. Binary fission produces two (binary) daughter cells that are identical to the original parent.Binary fission produces two (binary) daughter cells that are identical to the original parent.  Prokaryotes contain a single chromosome with only a few proteins.

44. Binary Fission

45. Review  Interphase  Mitotic Stage  Cell Cycle Control  Apoptosis  Mitosis  Mitosis in Animal Cells  Cytokinesis  Cancer  Prokaryotic Cell Division