2. Purpose of Mitosis To create two identical daughter cells from one parent cell Cells begin diploid (2 sets of chromosomes) and end diploid

3. Stages of the Cell Cycle G1 S G2 Mitosis Cytokenesis Interphase

4. The Steps Prior to Cell Division the cell doubles in size (G1 Phase) chromosomes replicate (S Phase) the number of organelles doubles –most doubling is directed by the nucleus

5. Replicated Chromosome

6. What is DNA Replication? A chromosome is unzipped and thus starts as one strand of DNA Each daughter cell needs its own copy of the DNA strand. The DNA strand is duplicated and the two parts are “ tied ” together.

7. Important Details DNA replication occurs DNA replication occurs during S phase, NOT mitosis during S phase, NOT mitosis Mitosis and cytokinesis Mitosis and cytokinesis overlap overlap

8. Important Details Cells can also enter a G 0 phaseCells can also enter a G 0 phase in which they no longer divide in which they no longer divide Cells move to the next stage when enough “trigger protein” has built upCells move to the next stage when enough “trigger protein” has built up

9. Cells of the adult central nervous system, (brain and spinal cord,) do NOT divide.

10. Cassius Clay Muhammad Ali

11. Christopher Reeve

12. Mitosis is the process of dividing just the nucleus (not the whole cell.) Prophase Metaphase Anaphase Telophase

14. Steps of MITOSIS PROPHASE 1. Nuclear membrane is broken down 2. Chromosomes appear 3. Centrioles migrate (plants DON ’ T have centrioles)

16. METAPHASE chromosomes align on the equatorial plane Spindle fibers attach to chromosomes Steps of MITOSIS

18. ANAPHASE chromatids move to opposite ends of the cell with the help of spindle fibers Steps of MITOSIS

20. TELOPHASE chromosomes stop moving and the nuclear membrane reforms Steps of MITOSIS

25. CYTOKINESIS Division of the entire cell after the nucleus divides Differs for plants and animals because plant cells have cell walls

27. Animal Cell Division the cell membrane constricts to make a groove and divide This groove is referred to as the cleavage furrow

28. Plant Cell Division Vesicles produced by golgi bodies form a midline in the cell Vesicles fuse to make a cell plate which attaches to cell wall

29. Mitosis Rap http://www.youtube.com/watch?v=pOsAbTi9tHw

30. How does the beginning cell differ from the ending cells?

31. Regulation of Cell Cycle  G1/S checkpoint  G2/M checkpoint  Tumor suppressor genes can control these checkpoints Tumor suppressor genes turn off or decrease rate of cell division

32. G 1 checkpoint G1G1 G2G2 G 2 checkpoint M checkpoint M S Control system Figure 12.15

33. For many cells, the G 1 checkpoint seems to be the most important If a cell receives a go-ahead signal at the G 1 checkpoint, it will usually divide If the cell does not receive the go-ahead signal, it will exit the cycle, switching into a nondividing state called the G 0 phase

34. Neighboring cells communicate with dividing cells to regulate their growth also.

35. Some of the genes that control cell division are called Proto-oncogenes. Proto-oncogenes encode proteins that function to stimulate cell division Important for normal human development and for the maintenance of tissues and organs.

36. Sometimes a proto-oncogene undergoes a mutation and becomes an oncogene.

37. Oncogenes and Cancer Cells When mutated into an oncogene it may produce a large amount of these growth proteins, resulting in excessive cell division. When a cell can no longer regulate its rate of cell division it becomes a Cancer Cell.

38. Because there are several genes that act as proto- oncogenes it may take 3-4 mutations to cause harm. Anything that can damage genes can cause these harmful mutations. – These are called carcinogens or mutagens.

39. Cancer is a disease of the cell cycle. Some of the body cells divide uncontrollably and tumors form. Tumors in Liver Tumor in Colon

40. DNA mutations disrupt the cell cycle. Mutations may be caused by: 1. radiation 2. smoking 3. Pollutants 4. chemicals 5. viruses

41. Due to DNA mutations, cancer cells ignore the chemical signals that start and stop the cell cycle.

42. Due to DNA mutations, cancer cells cannot communicate with neighboring cells. Cells continue to grow and form tumors. Skin cancer

43. SUMMARY Normal Cell Division 1.DNA is replicated properly. 2.Chemical signals start and stop the cell cycle. 3.Cells communicate with each other so they don’t become overcrowded. Cancer Cells 1. Mutations occur in the DNA when it is replicated. 2. Chemical signals that start and stop the cell cycle are ignored. 3. Cells do not communicate with each other and tumors form.

44. Cancer Tumor = loss of cell cycle control = abnormal growth of cells Benign = non-spreading Malignant = spreading Metastasis = spread rate of a malignant cancer to locations other than their origin (tumor cells enter blood vessels and travel to other parts of the body)

45. Environment and Cancer Solid relationship exists between environmental factors and cancer Cancer cluster: Large number of cases in restricted area –Epidemiologists examine environment for link Cancer cluster in Woburn, Massachusetts, –Environmental trigger, industrial solvents from contaminated well water

46. Skin Cancer ~1 million new cases in U.S. per year Almost all cases related to UV light exposure from sun or tanning lamps Lightly pigmented people higher risk –genetic characteristics can affect the susceptibility

47. Skin Cancer Ozone depletion also contributes to increased UV exposure and risk In spite of risk, some choose low SPF suntans and only 25% of Americans consistently use sunscreen

48. Smoking Related to cancers of oral cavity, larynx, esophagus, and lungs –Accounts for 30% of all cancer deaths –Most have very low survival rate (e.g. 13% lung cancer sufferers survive beyond 5 yrs)