2. Two Types  Mitosis  Used for growth, repair, and asexual reproduction  Results in 2 exact copies of the original cell  Meiosis (next chapter)  Used in sexual reproduction  Results in cells with ½ the number of chromosomes of the original cells  More on this later.

3. Mitosis  Starts with 1 cell, results in 2 cells that are exact copies of the original.  Four phases:  Prophase  Metaphase  Anaphase  Telophase

4. Prophase  Chromatin coils to form chromosomes  Nucleolus and Nuclear membrane breaks down  Centrioles move away from each other toward the poles (animals only).  Spindle fibers form

5. Metaphase  Chromosomes are moved to the equator by spindle fibers.

6. Anaphase  Sister chromatids separate.  Separated chromatids (now called daughter chromosomes) move toward the poles.

7. Telophase  Spindle fibers break down.  Chromosomes unwind to form of chromatin.  Nuclear membrane and nucleolus reform.

8. Which phase? Metaphase

9. Which phase? Telophase

10. Which phase? Anaphase

11. Which phase? Prophase

12. Animations http://www.cellsalive.com/mitosis.htm

13. Cytokinesis  The physical division of the cytoplasm.  Animals pinch their cell membrane inward until 2 cells are formed.  Plants form a “cell plate” to form a new cell.

15. Control of the cell cycle

16. Control of the Cell Cycle  Not all cells follow the cell cycle at the same rate.  Skin cells  Liver cells  Nerve cells

17. Control of the Cell Cycle  Normal cells:  Divide until they come in contact with one another, then stop when they become too crowded.  Only grow when connected to something.  Respond to internal and external signals  Many molecules control the cell cycle from inside the cell and from outside the cell.  “Cyclins” and Growth Factors are two examples of these molecules (they act like stop and go signals).

18. Control of the Cell Cycle  Cancer Cells:  Have lost control of the cell cycle.  Do not respond the system of chemical signals  Do not stop dividing when in contact with other cells.  Can move from one place in the body to another.  Interrupts normal tissue activity.

19. Cancer Terms  Tumor – a mass or lump of cells resulting from uncontrolled cell division.  Benign tumor – tumor that does not spread to other areas.  Malignant tumor – invades surrounding tissues  Apoptosis – programmed cell death (normal)  Cancer cells do not respond to this.

21. Causes of cancer  Caused by anything that changes the DNA responsible for controlling the cell cycle.  Tobacco  Radiation  Sunlight  Viral infections  Random mutation

22. Treatments  Remove tumor by surgery if possible.  Radiation treatment  Chemotherapy

23. Cell Differentiation  Zygote – a fertilized egg  Differentiation – process in which cells become specialized.

24. Stem cells  Undifferentiated cells  The zygote and the first few cells that arise from it can become any type of cell.  Totipotent cell – a cell that can become any type of cell  The zygote develops into a blastocyst.  Pluripotent cell – a cell that can become most, but not all types of cells. Undifferentiated cells

25. Stem Cells continued  Embryonic stem cells are the cells found in the early embryo  Are pluripotent

26. Stem cells continued  Adult stem cells are cells that replace certain types of cells in our bodies when needed.  Multipotent cell – has a limited potential to develop into many types of cells  Ex. Adult stem cells in the bone marrow can develop into any type of blood cell (red, white, or platelets.

27. Stem cells continued  Benefits of stem cell research?  Ethical issues? Ethical issues?