1. February 26, 2015 Objective:  Model the stages of mitosis  Explain the cell cycle Journal: Why are cells small?

2. The Cell Cycle

3. Four Phases  G1 – Gap 1  S – DNA Replication  G2 – Gap 2  Mitosis

4. Interphase Occurs when the cell is not dividing Cells spend the majority of their time in this phase Made up of three phases  G1 – Growth Phase  S – DNA Replication Occurs Chromatin replicates to form sister chromatids  G2 – Growth Phase

5. Interphase continued… During G2, specialized structures are made:  Centrioles – help to make spindle fibers  Spindle fibers – strings that attach to chromosomes and help move them within the cell

6. Mitosis Division of the nucleus Occurs in 4 stages: PMAT  Prophase  Metaphase  Anaphase  Telophase http://www.stolaf.edu/people/giannini/flashanim at/celldivision/crome3.swf

7. 1st: Prophase Mitosis begins and cell begins to divide Centrioles begin to move to opposite ends of cell Spindle fibers form from the centrioles

8. Prophase

9. 2nd: Metaphase Sister Chromatids or pairs of chromosomes line up at the center of the cell and attach to the spindle fibers

10. Metaphase

11. 3rd: Anaphase Sister chromatids separate and begin to move to opposite ends of the cell

12. Anaphase

13. 4 th : Telophase Two new nuclei form around the chromosomes Chromosomes become chromatin (threads rather than X’s) Mitosis ends

14. Telophase

15. Cytokinesis Last stage of the cell cycle  Not part of mitosis Cell membrane pinches inwards to create two daughter cells – each with its own nucleus with identical chromosomes

16. Cytokinesis