Mitosis

1. Mitosis Cell division This Powerpoint is hosted on www.worldofteaching.com Please visit for 1000+ free powerpoints

2. Cell division All complex organisms originated from a single fertilised egg. Every cell in your body started here, through cell division the numbers are increased Cell then specialize and change into their various roles

3. Mitosis • Mitosis is the process by which new body cell are produced for: • Growth • Replacing damaged or old cells. This is a complex process requiring different stages

4. Cell division starts in the nucleus. The nucleus is made up of a mass of long, thin intertwined chromosomes called chromatin. The chromosomes are in homologous pairs - chromosomes that are the same size and shape and have the same genes. This stage is known as interphase.

5. Single Chromosome

6. Interphase • Interesting things happen! • Cell preparing to divide • Genetic material doubles

7. These chromosomes must be equally distributed to daughter nuclei during mitosis. • The two phases that the cell goes through are known as the cell cycle.

8. Cell Cycle 2 hours 4 hours 4 hours 10 hours

9. Mitosis • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis

10. Prophase • Chromosome pair up! • Chromosomes thicken and shorten -become visible -2 chromatids joined by a centromere • Centrioles move to the opposite sides of the nucleus • Nucleolus disappears • Nuclear membrane disintegrate

12. Metaphase • Chromosomes meet in the middle! • Chromosomes arrange at equator of cell • Become attached to spindle fibres by centromeres • Homologous chromosomes do not associate

14. Anaphase • Chromosomes get pulled apart • Spindle fibres contract pulling chromatids to the opposite poles of the cell

15. Telophase • Now there are two! • Chromosomes uncoil • Spindle fibres disintegrate • Centrioles replicate • Nuclear membrane forms

17. Cytokinesis • Animal – • Begins near the end of anaphase & finishes during telophase • Pinching in (cleavage furrow) of cell membrane at the middle of the cell to form two daughter cells of same size

19. Cytokinesis cont’d • Plant – • No centrioles so no asters • Spindle forms from end of cell • No pinching – cell plate forms across the middle of the cell which develops into cell wall

22. Parent cell Chromosomes are copied and double in number Chromosomes now split 2 daughter cells identical to original

23. Mitosis • All daughter cells contain the same genetic information from the original parent cell from which it was copied. • Every different type cell in your body contains the same genes, but only some act to make the cells specialise – e.g. into nerve or muscle tissue.

24. Mitosis – bone cell slides 2 1 Cells split Chromosomes copied Parent cell 3 4 5 2 daughter cells Copies separating

25. Plants

26. Rat – epithelial cells

27. Mitosis: An Interactive Animation

28. To remember the order of phases • Paco • Makes • A • Taco • Crunchy

29. Mitosis Regulation What regulates cell division? Do cells divide constantly? • Normal cells divide repeatedly until they come into contact with another cell. Then division will stop. Isolated cell divide until all the space they are in fills with cells

30. Uncontrolled growth Cancer – what is it? • Abnormal cells that reproduce in an uncontrolled way and eventually crowd out normal cells, destroying tissues and organs – tumor • Abnormal cells differ in shape to normal cells – known as malignant cells (any body cell can become malignant) • Any non cancerous tumor is benign

31. Cancer What causes the uncontrolled growth? • Caused by genetic mutations caused by: • Cancer causing genes – oncogenes • Some are inherited, some from viruses, mutated genes • Carcinogens – cancer causing substances in the environment (tobacco smoke, asbestos, saccharin, lead, mustard gas, prolonged exposure to X-rays, ultraviolet light

32. Metastasis • Spread of cancer from original site to elsewhere • Usually can migrate to the lymph nodes near the site of the original cancer

33. Figure 3 - The stages of tumor development. A malignant tumor develops across time, as shown in this diagram. This tumor develops as a result of four mutations, but the number of mutations involved in other types of tumors can vary. We do not know the exact number of mutations required for a normal cell to become a fully malignant cell, but the number is probably less than ten. a. The tumor begins to develop when a cell experiences a mutation that makes the cell more likely to divide than it normally would. b. The altered cell and its descendants grow and divide too often, a condition called hyperplasia. At some point, one of these cells experiences another mutation that further increases its tendency to divide. c. This cell's descendants divide excessively and look abnormal, a condition called dysplasia. As time passes, one of the cells experiences yet another mutation. d. This cell and its descendants are very abnormal in both growth and appearance. If the tumor that has formed from these cells is still contained within its tissue of origin, it is called in situ cancer. In situ cancer may remain contained indefinitely. e. If some cells experience additional mutations that allow the tumor to invade neighboring tissues and shed cells into the blood or lymph, the tumor is said to be malignant. The escaped cells may establish new tumors (metastases) at other locations in the body.

34. Cancer Treatments • Surgery • Remove the cancer and a portion of healthy tissue from around the cancer – try to ensure that no cancer cells remain

35. Cancer Treatments • Chemotherapy • Systemic – medications that interfere with cell division. (Freeze spindle, spindle does not form) • Kills rapidly dividing cells – intestinal cells, hair follicle cells, blood cells (nausea, hair loss, low immunity)

37. Cancer Treatments • Radiation • Local – high energy radiation which disrupts cell division. • Destroys cancer cells without damaging other cells