1. Cell Cycle Life of a Eukaryotic Cell

2. Cell Cycle

3. (Interphase in Red) G1 – cell grows & carries out major functions S – DNA is copied G2 – Prep for mitosis; organelles reproduced Mitosis – Nucleus divided into two nuclei, each with same number and kind of chromosomes Cytokinesis – cytoplasm divides

4. Cell Cycle Control How does cell “know” when to divide? Cell cycle controlled by many proteins (enzymes) at three main checkpoints: G1 checkpoint – decision made whether cell will divide (cell healthy and large enough). Some types of cell never pass this point (nerve, muscle) G2 checkpoint – Did DNA replication go OK? If so, go on to mitosis Mitosis checkpoint – Is mitosis over? If so, head to G1 phase

5. Cancer - What happens if control is lost Cancer = uncontrolled cell growth Disorder of cell division Control mechanisms don’t work (gene for proteins that control cell cycle are defective) Mutations: Overproduction of growth- promoting hormones – speeds up cell cycle Inactivation the control proteins that act to slow or stop cell cycle

6. Mitosis and Cytokinesis Chromatids are physically moved to opposite sides of dividing cells with help of spindle fibers Centrosome (in animals) – made up of two centrioles - organizes assembly of spindle fibers Spindle fibers made from microtubules

7. Mitosis and Cytokinesis Chromatids separate by attaching spindle fibers Spindle fibers attach to centromeres of chromosomes Paired chromatids separate. One chromatid goes to one pole of the cell, the other chromatid goes to the other as the spindle fibers shorten

8. Interphase (90% of cell’s time) Mitosis (nuclear division) Prophase Metaphase Anaphase Telophase Cytokinesis (cytoplasmic division) Watch video clip of mitosis

9. Another View of Mitosis

10. Mitosis Foldable 6 sheets of paper Follow teacher’s instructions to construct booklet You will make foldable based on pictures and descriptions of interphase, cyokinesis, and mitosis in your book (p. 125 and pp 130 – 132) Include sketches and textual descriptions in foldable You can also use www.cellsalive.com and www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/m ain.htmlwww.cellsalive.com

11. Headings for foldable Cover = Phases of Somatic Cell Division Following sheets – Interphase G1 S G2 Mitosis Prophase Metaphase Anaphase Telophase Cytokinesis

12. Homework Read Ch. 7 – “Meiosis and Sexual Reproduction” Also read about plant reproduction pp. 534 – 535, and pp. 538 – 539 Complete Guided Reading packet for Chapter 7 Complete Foldable