2. The Cell Cycle and Mitosis

3. IMPORTANCE 1. Growth 2. Tissue Repair 3. Means of asexual reproduction for single celled eukaryotes. 4. Keeps chromosome number constant.

4. Cell Cycle Interphase Mitosis Cytokinesis

5. Eukaryotic Cell Cycle 1. Most of cell cycle consists of the interphase 2. Mitosis describes nuclear division

6. INTERPHASE (Growth Phase) 1. Cell grows 2. Chromosomes duplicate. (Chromosomes consist of two DNA strands). 3. Cell prepares for mitosis

7. STAGES OF MITOSIS Mitosis= Nuclear Division Has 4 phases Prophase Metaphase Anaphase Telophase

8. PROPHASE 1. Chromosomes coil up and become visible 2. Nuclear membrane and Nucleolus disappears. (shown by dotted line) 3. Spindle appears. 4. Centrioles move toward poles

9. Early Prophase Late Prophase What has happened?

10. What’s a spindle? Made of the centriole and microtubules (part of the cytoskeleton) The fibers attach to the centromere of the chromosome and “reel them in” Interpretive Dance Time

11. METAPHASE Chromosomes become aligned at the equator of the spindle.

12. ANAPHASE 1. Chromatids separate. 2. Two identical groups formed. 3. Separated chromatids move to opposite poles of the cell.

13. TELOPHASE 1. Chromosomes uncoil and disappear 2. Nuclear membrane reappears. 3. In plant cells the cell plate appears. Spindle fibers dissolve

14. The cytoplasm is divided and produces two daughter cells (identical). Cytokinesis (Division of Cytoplasm)

15. Animation

16. CRITICAL THINKING Human red blood cells develop in the bone marrow from stem cells, and lose their nucleus before maturing and being released into the bloodstream. While this gives a cell that can be densely packed with hemoglobin molecules, what are the consequences as for as the longevity & its ability to replicate?

17. CRITICAL THINKING Lacking DNA coding, the red blood cells will not themselves be able to replicate and we must rely on the stem cells in the bone marrow to continue red blood cell production. In addition, the red blood cells will be limited in life span and unable to make substantial DNA- coded repairs.

18. Did You KnowDid You Know… Cells do not live forever, and they will reach a point where they will divide through mitosis, or die through a process called apoptosis. Cancer cells are the exception, these cells do not die and divide uncontrollably as they crowd out healthy, productive cells. Cancer can have many causes, but most are thought to be related to carcinogens in the environment. Carcinogens are chemicals that can damage DNA and interfere with a cell's normal cycle, thus disrupting the cells ability to control when and how often it divides.