Cell Growth, Division, and Reproduction - Overview and Process

1. Lesson Overview 10.1 Cell Growth, Division, and Reproduction

2. THINK ABOUT IT • When a living thing grows, what happens to its cells? • What is there about growth that requires cells to divide and reproduce themselves?

3. Limits to Cell Size • What are some of the difficulties a cell faces as it increases in size?

4. Information “Overload” • Compare a cell to a growing town. The town library has a limited number of books. As the town grows, these limited number of books are in greater demand, which limits access. • A growing cell makes greater demands on its genetic “library.” If the cell gets too big, the DNA would not be able to serve the needs of the growing cell.

5. Traffic Problems • To use the town analogy again, as the town grows, more and more traffic clogs the main street. It becomes difficult to get information across town and goods in and out. • Similarly, a cell that continues to grow would experience “traffic” problems. If the cell got too large, it would be more difficult to get oxygen and nutrients in and waste out.

6. Division of the Cell • Before a cell grows too large, it divides into two new “daughter” cells in a process called cell division. • Before cell division, the cell copies all of its DNA. • It then divides into two “daughter” cells. Each daughter cell receives a complete set of DNA. • Cell division reduces cell volume. It also results in an increased ratio of surface area to volume, for each daughter cell.

7. Lesson Overview 10.2 The Process of Cell Division

8. THINK ABOUT IT What role does cell division play in your life? Does cell division stop when you are finished growing?

9. Chromosomes What is the role of chromosomes in cell division?

10. Chromosomes What is the role of chromosomes in cell division? Chromosomes make it possible to separate DNA precisely during cell division.

11. The genetic information that is passed on from one generation of cells to the next is carried by chromosomes. Every cell must copy its genetic information before cell division begins. Each daughter cell gets its own copy of that genetic information. Cells of every organism have a specific number of chromosomes. Chromosomes

12. The Cell Cycle What are the main events of the cell cycle?

13. The Cell Cycle What are the main events of the cell cycle? During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells.

14. The Eukaryotic Cell Cycle The eukaryotic cell cycle consists of four phases: G1, S, G2, and M. Interphase is the time between cell divisions. It is a period of growth that consists of the G1, S, and G2 phases. The M phase is the period of cell division.

15. G1 Phase: Cell Growth In the G1 phase, cells increase in size and synthesize new proteins and organelles.

16. S Phase: DNA Replication In the S (or synthesis) phase, new DNA is synthesized when the chromosomes are replicated.

17. G2 Phase: Preparing for Cell Division In the G2 phase, many of the organelles and molecules required for cell division are produced.

18. M Phase: Cell Division In eukaryotes, cell division occurs in two stages: mitosis and cytokinesis. Mitosis is the division of the cell nucleus. Cytokinesis is the division of the cytoplasm.

19. Important Cell Structures Involved in Mitosis Chromatid – each strand of a duplicated chromosome Centromere – the area where each pair of chromatids is joined Centrioles – tiny structures located in the cytoplasm of animal cells that help organize the spindle Spindle – a fanlike microtubule structure that helps separate the chromatids

20. Mitosis What events occur during each of the four phases of mitosis?

21. Mitosis What events occur during each of the four phases of mitosis? During prophase, the genetic material inside the nucleus condenses and the duplicated chromosomes become visible. Outside the nucleus, a spindle starts to form.

22. Prophase During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible.

23. Prophase During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible. The centrioles move to opposite sides of nucleus and help organize the spindle.

24. Prophase During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible. The centrioles move to opposite sides of nucleus and help organize the spindle. The spindle forms and DNA strands attach at a point called their centromere.

25. Prophase During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible. The centrioles move to opposite sides of nucleus and help organize the spindle. The spindle forms and DNA strands attach at a point called their centromere. The nucleolus disappears and nuclear envelope breaks down.

26. Mitosis What events occur during each of the four phases of mitosis? During metaphase, the centromeres of the duplicated chromosomes line up across the center of the cell. Spindle fibers connect the centromere of each chromosome to the two poles of the spindle.

27. Metaphase During metaphase, the second phase of mitosis, the centromeres of the duplicated chromosomes line up across the center of the cell.

28. Metaphase During metaphase, the second phase of mitosis, the centromeres of the duplicated chromosomes line up across the center of the cell. The spindle fibers connect the centromere of each chromosome to the two poles of the spindle.

29. Mitosis What events occur during each of the four phases of mitosis? During anaphase, the chromosomes separate and move along spindle fibers to opposite ends of the cell.

30. Anaphase During anaphase, the third phase of mitosis, the centromeres are pulled apart and the chromatids separate to become individual chromosomes.

31. Telophase During telophase, the fourth and final phase of mitosis, the chromosomes spread out into a tangle of chromatin.

32. Anaphase During anaphase, the third phase of mitosis, the centromeres are pulled apart and the chromatids separate to become individual chromosomes. The chromosomes separate into two groups near the poles of the spindle.

33. Mitosis What events occur during each of the four phases of mitosis? During telophase, the chromosomes, which were distinct and condensed, begin to spread out into a tangle of chromatin.

34. Telophase During telophase, the fourth and final phase of mitosis, the chromosomes spread out into a tangle of chromatin. A nuclear envelope re-forms around each cluster of chromosomes.

35. Telophase During telophase, the fourth and final phase of mitosis, the chromosomes spread out into a tangle of chromatin. A nuclear envelope re-forms around each cluster of chromosomes. The spindle breaks apart, and a nucleolus becomes visible in each daughter nucleus.

36. Cytokinesis How do daughter cells split apart after mitosis?

37. Cytokinesis How do daughter cells split apart after mitosis? Cytokinesis completes the process of cell division – it splits one cell into two.

38. Cytokinesis is the division of the cytoplasm. The process of cytokinesis is different in animal and plant cells. Cytokinesis

39. Cytokinesis in Animal Cells The cell membrane is drawn in until the cytoplasm is pinched into two equal parts. Each part contains its own nucleus and organelles.

40. Cytokinesis in Plant Cells In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall. Instead, a cell plate forms between the divided nuclei that develops into cell membranes. A cell wall then forms in between the two new membranes.

41. The Stages of the Cell Cycle

42. Cancer: Uncontrolled Cell Growth How do cancer cells differ from other cells?

43. Cancer: Uncontrolled Cell Growth How do cancer cells differ from other cells? Cancer cells do not respond to the signals that regulate the growth of most cells. As a result, the cells divide uncontrollably.

44. Cancer is a disorder in which body cells lose the ability to control cell growth. Cancer cells divide uncontrollably to form a mass of cells called a tumor.

45. A benign tumor is noncancerous. It does not spread to surrounding healthy tissue. • A malignant tumor is cancerous. It invades and destroys surrounding healthy tissue and can spread to other parts of the body. The spread of cancer cells is called metastasis. Cancer cells absorb nutrients needed by other cells, block nerve connections, and prevent organs from functioning.

46. What Causes Cancer? Cancers are caused by defects in genes that regulate cell growth and division. Some sources of gene defects are smoking tobacco, radiation exposure, defective genes, and viral infection. A damaged or defective p53 gene is common in cancer cells. It causes cells to lose the information needed to respond to growth signals.

47. Treatments for Cancer Some localized tumors can be removed by surgery. Many tumors can be treated with targeted radiation. Chemotherapy is the use of compounds that kill or slow the growth of cancer cells.

48. Lesson Overview 10.4 Cell Differentiation

49. THINK ABOUT IT The human body contains hundreds of different cell types, and every one of them develops from the single cell that starts the process. How do the cells get to be so different from each other?

50. From One Cell to Many How do cells become specialized for different functions?