2. Section 9-3

3. Normal Cell Cycle  Different cyclin/CDK combinations signal other activities, including DNA replication, protein synthesis, and nuclear division throughout the cell cycle.

4. Quality Control Checkpoints  The cell cycle has built-in checkpoints that monitor the cycle and can stop it if something goes wrong.  Spindle checkpoints also have been identified in mitosis.

5. Abnormal Cell Cycle: Cancer  Cancer is the uncontrolled growth and division of cells.  Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function

6. Causes of Cancer  The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations.  Various environmental factors can affect the occurrence of cancer cells.

7. Apoptosis  Programmed cell death  Cells going through apoptosis actually shrink and shrivel in a controlled process.

8. Stem Cells  Unspecialized cells that can develop into specialized cells when under the right conditions

9. Embryonic Stem Cells  After fertilization, the resulting mass of cells divides repeatedly until there are about 100–150 cells. These cells have not become specialized.

10. Adult Stem Cells  Found in various tissues in the body and might be used to maintain and repair the same kind of tissue  Less controversial because the adult stem cells can be obtained with the consent of their donor.

11. 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 for its the longevity & its ability to replicate?

12. CRITICAL THINKING Lacking DNA coding, the red blood cells will not 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.