1. Cell Division Ch. 10 Biology Ms. Haut

2. 1.Replacement of lost or damaged cells 2.Growth—multicellular organisms grow and develop from single cell (fertilize egg) 3.Cell Reproduction Functions of Cell Divsion

3. Prokaryotes Genes usually carried on a single circular DNA molecule DNA has a few proteins and is attached to the plasma membrane at one point DNA not bounded by membrane (nucleoid region) Cells divide by binary fission http://www.karlloren.com/biopsy/images/TEM-Fission_rod.jpg

4. Binary Fission Before dividing, an exact copy of the chromosome is made The attachment point divides so the 2 new chromosomes are attached at separate parts of the membrane The cell elongates and a new plasma membrane is added and the attachment points move apart The plasma membrane and new cell wall pinch through the cell, separating the 2 chromosomes into two new, identical cells Copyright © 2001 Pearson Education, Inc. publishing Benjamin Cummings

5. Cell Division in Eukaryotes In eukaryotes, cell division occurs in two major stages. The first stage, division of the cell nucleus, is called mitosis. The second stage, division of the cell cytoplasm, is called cytokinesis. Copyright Pearson Prentice Hall

6. Chromosomes Genetic information is passed from one generation to the next on chromosomes. Before cell division, each chromosome is duplicated, or copied. Copyright Pearson Prentice Hall http://www.anselm.edu/homepage/jpitocch/genbio/sphase.JPG

7. Chromosomes Each chromosome consists of two identical “sister” chromatids. Each pair of chromatids is attached at an area called the centromere. Copyright Pearson Prentice Hall http://www.uic.edu/classes/bios/bios100/labs/realchromo.jpeg

8. Chromosomes When the cell divides, the chromatids separate. Each new cell gets one chromatid. Copyright Pearson Prentice Hall http://www.anselm.edu/homepage/jpitocch/genbio/sphase.JPG

9. Copyright Pearson Prentice Hall The Cell Cycle The cell cycle is the series of events that cells go through as they grow and divide. Interphase is the period of growth that occurs between cell divisions. http://www.pitt.edu/~super1/lecture/lec19281/img004.GIF

10. Copyright Pearson Prentice Hall During the Cell Cycle a cell grows prepares for division divides to form two daughter cells, each of which begins the cycle again http://www.pitt.edu/~super1/lecture/lec19281/img004.GIF

11. The Cell Cycle The cell cycle consists of four phases: – G 1 (First Gap Phase) – S Phase – G 2 (Second Gap Phase) – M Phase Copyright Pearson Prentice Hall

12. Events of the Cell Cycle During G 1 phase (First Gap Phase) – the cell increases in size – synthesizes new proteins and organelles Copyright Pearson Prentice Hall http://media.photobucket.com/image/interphase%20stages/udyama/cycle.gif

13. Events of the Cell Cycle During the S phase, – chromosomes are replicated – DNA synthesis takes place – Once a cell enters the S phase, it usually completes the rest of the cell cycle. Copyright Pearson Prentice Hall http://media.photobucket.com/image/interphase%20stages/udyama/cycle.gif

14. Events of the Cell Cycle The G 2 phase (Second Gap Phase) organelles and molecules required for cell division are produced Once G 2 is complete, the cell is ready to start the M phase— Mitosis Copyright Pearson Prentice Hall http://media.photobucket.com/image/interphase%20stages/udyama/cycle.gif

15. Copyright Pearson Prentice Hall Mitosis – Biologists divide the events of mitosis into four phases: Prophase Metaphase Anaphase Telophase

16. Prophase Prophase is the first and longest phase of mitosis. The centrioles separate and take up positions on opposite sides of the nucleus.

17. Prophase The centrioles lie in a region called the centrosome. The centrosome helps to organize the spindle, a fanlike microtubule structure that helps separate the chromosomes.

18. Prophase Chromatin condenses into chromosomes. The centrioles separate and a spindle begins to form. The nuclear envelope breaks down.

19. Prophase http://micro.magnet.fsu.edu/cells/fluorescencemitosis/images/prophasesmall.jpg

20. Metaphase Centrosomes at opposite poles of cell The chromosomes line up across the center of the cell. Centromeres of all chromosomes are aligned with one another, and sister chromatids straddle metaphase plate Microtubules connect the centromere of each chromosome to the poles of the spindle. Mitotic spindle completely formed

21. Metaphase http://micro.magnet.fsu.edu/cells/fluorescencemitosis/images/

22. Anaphase The sister chromatids separate into individual chromosomes. The chromosomes continue to move until they have separated into two groups.

23. Anaphase http://micro.magnet.fsu.edu/cells/fluorescencemitosis/images/

24. Telophase and Cytokinesis Daughter nuclei form at two poles of cell A new nuclear envelope forms around each cluster of chromosomes. Chromosomes gather at opposite ends of the cell and uncoil back into chromatin Mitotic spindle disappears Nucleolus reforms

25. Telophase http://micro.magnet.fsu.edu/cells/fluorescencemitosis/images/

26. Cytokinesis During cytokinesis, the cytoplasm pinches in half. Process overlaps with telophase of mitosis Each daughter cell has an identical set of duplicate chromosomes Copyright Pearson Prentice Hall

27. Cytokinesis Occurs differently in plants and animals – Cleavage furrow forms in animal cells – Cell plate forms in plant cells Cleavage furrow Cell Plate

28. Cytokinesis Figure 8.9bFigure 8.9a

29. Cell Division

30. Copyright Pearson Prentice Hall The series of events that cells go through as they grow and divide is called a)the cell cycle. b)mitosis. c)interphase. d)cytokinesis.

31. Copyright Pearson Prentice Hall The phase of mitosis during which the chromosomes line up across the center of the cell is a)prophase. b)metaphase. c)anaphase. d)telophase.

32. Copyright Pearson Prentice Hall Cytokinesis usually occurs a)at the same time as telophase. b)after telophase. c)during interphase. d)during anaphase

33. Copyright Pearson Prentice Hall DNA replication takes place during the a)G 2 phase of the cell cycle. b)G 1 phase of the cell cycle. c)S phase of the cell cycle. d)M phase of the cell cycle.

34. Copyright Pearson Prentice Hall During mitosis, “sister” chromatids separate from one another during a)telophase. b)interphase. c)anaphase. d)metaphase.

35. END OF SECTION

36. Cell Cycle Regulation Ch. 10 Biology Ms. Haut

37. Controls on Cell Division Experiments show that normal cells will reproduce until they come into contact with other cells. When cells come into contact with other cells, they respond by not growing. This demonstrates that controls on cell growth and division can be turned on and off. Copyright Pearson Prentice Hall

38. Controls on Cell Division Contact Inhibition Cells attach to dish surface and divide. When cells have formed a complete single layer, they stop dividing (contact inhibition). If some cells are scraped away, the remaining cells divide to fill the dish with a single layer and then stop (contact inhibition).

39. Cell Cycle Regulators The cell cycle is regulated by a specific protein. The amount of this protein in the cell rises and falls in time with the cell cycle. Scientists called this protein cyclin because it seemed to regulate the cell cycle. Cyclins regulate the timing of the cell cycle in eukaryotic cells. Copyright Pearson Prentice Hall

40. Internal Regulators Proteins that respond to events inside the cell are called internal regulators. Internal regulators allow the cell cycle to proceed only when certain processes have happened inside the cell. – Cells do not enter into Mitosis until all chromosomes have been copied – Anaphase does not occur until all chromosomes are lined up on metaphase plate and attached to the mitotic spindle Copyright Pearson Prentice Hall

41. External Regulators Proteins that respond to events outside the cell are called external regulators. External regulators direct cells to speed up or slow down the cell cycle.

42. External Regulators Growth factors are proteins that stimulate growth and division After forming a single layer, cells have stopped dividing. Providing an additional supply of growth factors stimulates further cell division.

43. External Regulators Other molecules found on the surfaces of neighboring cells can slow down or stop their cell division – Prevents excessive cell growth and keeps tissues in the body from disrupting one another

44. Uncontrolled Cell Growth Cancer is a disorder in which some of the body's own cells lose the ability to control growth. Cancer cells do not respond to the signals that regulate the growth of most cells. Copyright Pearson Prentice Hall http://www.beliefnet.com/healthandhealing/images/Cancer_cell_division.jpg

45. Copyright Pearson Prentice Hall Uncontrolled Cell Growth Cancer cells divide uncontrollably and form masses of cells called tumors that can damage the surrounding tissues. Cancer cells may break loose from tumors and spread throughout the body, disrupting normal activities and causing serious medical problems or even death. http://images.google.com/imgres?imgurl=http://ww w.mmshealthyforlife.com/wp- content/uploads/2009/04/cancer_cells_splitting.jpg&i mgrefurl=http://www.mmshealthyforlife.com/

46. Uncontrolled Cell Growth Two types of tumors – Benign tumors Grow only locally Do not spread Can typically be removed – Malignant tumors Grow and invade neighboring tissues Can break away from original tumor and spread throughout the body (metastasis)

47. Uncontrolled Cell Growth An astonishing number of cancer cells have a defect in a gene called p53 p53 is a tumor suppressing gene found on chromosome 17 – Prevents mitosis if DNA is damaged – Will activate other genes to stop cell growth or cause cell death http://www.hhmi.org/biointeractive/cancer/p53/01.html

48. Risks of Cancer Tobacco (lung cancer, lip and mouth cancer) Sunlight (UV radiation leading to skin cancer) Ionizing radiation (X-rays) Certain chemicals and other substances (asbestos, benzene, certain metals, etc.) Some viruses and bacteria (liver cancer, lymphoma, leukemia) Alcohol (liver cancer, breast cancer) Poor diet, lack of physical activity, or being overweight Growing older Family history of cancer www. cancer.gov

49. Cell Cycle Regulation

50. Copyright Pearson Prentice Hall The cell cycle is believed to be controlled by proteins called a)spindles. b)cyclins. c)regulators. d)centrosomes.

51. Copyright Pearson Prentice Hall Proteins that respond to events inside the cell are called a)internal regulators. b)external regulators. c)cyclins. d)growth factors.

52. Copyright Pearson Prentice Hall One of the functions of internal regulators is to a)cause the cell to stop dividing. b)prevent anaphase from occurring until all chromosomes are attached to the spindle. c)trigger cancer formation. d)undergo cell division randomly.

53. Copyright Pearson Prentice Hall One effect of an internal regulator is that a cell will not begin mitosis until a)it becomes too large. b)the cell’s growth is stimulated. c)it is in physical contact with other cells. d)all its chromosomes have been replicated.

54. Copyright Pearson Prentice Hall One factor common to almost all cancer cells is a)a lack of cyclin. b)a defect in gene p53. c)exposure to tobacco smoke. d)exposure to radiation.