1. Cell Cycle and Mitosis pp.149-151

2. ChromosomalDNA molecules Chromosomes Figure 12.5-3 Centromere 1 Chromosomearm Chromosome duplication(including DNA replication)and condensation 2 Sisterchromatids Separation of sisterchromatids intotwo chromosomes 3

3. Cell Cycle • 3 major phases • Interphase: time between cell divisions • G phases: growth • S phase: copying of DNA • M phase (mitosis): division of the nucleus • Cytokinesis: division of the cytoplasm

4. Mitosis (M phase)

5. Mitosis (M phase) • 2n  “4n”  2 (2n) • Continuous process starts with interphase • Separate the doubled chromosomes • Four phases • prophase  metaphase  anaphase  telophase

6. Prophase • Can see chromosomes • Chromatids stay connected by centromeres • Nuclear membrane break down • Centrosomes and centrioles appear and early mitotic spindle forms

7. Metaphase • Two types of fibers (mitotic spindle) • kinetochore fibers: attach to centromere of chromosome • polar fibers: extend centrosome to centrosome, push cell apart • Fibers line up the chromosomes in middle

8. Anaphase • Chromatids are pulled apart by fibers • Move towards opposite poles of dividing cells

9. Telophase • Chromosomes in opposite ends • Spindle fibers break down • Nucleus reforms • Cytokinesis

10. MOVIE