2.  Growth  Reproduction  Repair Why do cells divide?

3. Cell Cycle 3 Phases of Cell Cycle  Interphase—Cell preparation  Mitosis—Cell division  Cytokinesis—Cell splits into two

4.  DNA is in the form of long Fibers that cannot be seen, called chromatin  DNA replicates  Organelles double  Cell grows in size  Centrioles form  Centrioles are part of the animal cell that forms the mitotic spindle that DNA will line up on during mitosis Interphase

5.  DNA tightens and condenses to form chromosomes  Centrioles move to opposites sides of the cell  Nuclear membrane begins to disappear  Chromosomes line up with their duplicated pair and are attached at the center—called the centromere  The chromosome and its identical pair are now called sister chromatids 1 st stage of mitosis: Prophase

6.  Nucleus has disappeared completely  Sister chromatids line up along the middle plane of the cell (called the equator)  Mitotic spindle is now fully formed The mitotic spindle are the fibers that are formed from the centrioles and hold the sister chromatids in place 2 nd stage of mitosis: Metaphase

7.  Two chromatids separate  Each pole of the cell now has a complete set of DNA 3 rd phase of mitosis: Anaphase

8.  Nuclei begin to form at both ends of the cell  Chromosomes uncoil  Cleavage furrow forms—the indent in the cell membrane that begins the separation into two cells  Cytokinesis begins and cell membrane begins to separate 4 th stage of mitosis: Telophase

9.  The two cells now divide completely  The result is two cells that are identical to each other and have a complete set of DNA  When a cell has a complete set of DNA we say that it is a diploid cell Cytokinesis

10. The Whole Picture

11.  http://www.biology.arizona.edu/cell_bio/activities/cell _cycle/assignment.html http://www.biology.arizona.edu/cell_bio/activities/cell _cycle/assignment.html Onion Root Experiment