1. Warm-up 12/2: Why do cells replicate their DNA? When do cells replicate their DNA? What is the primary purpose of DNA?

2. Chromosomes pp. 151-153 Cell Cycle and Mitosis pp.154- 158

3. Chromosomes: coiled and compact DNA in nucleus DNA wrapped tightly around proteins called histones chromatids: two halves of a dividing chromosome Chromatids joined by a centromere

5. Chromosome number: each organism has a specific number of chromosomes Sex chromosomes: determine sex of the organism (X or Y) female: XX male: XY Autosomes: all other chromosomes All organisms have two copies that are homologous

6. Cell Cycle and Mitosis

7. 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

8. Mitosis (M phase) 2n  4n  2 (2n) Continuous process starts with interphase Need to separate the doubled chromosomes Four phases prophase  metaphase  anaphase  telophase PMAT

9. Prophase Can see chromosomes Chromatids stay connected by centromeres Nucleolus and nuclear membrane break down Centrosomes and centrioles appear Early mitotic spindle forms

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

11. Anaphase Chromatids of each chromosomes are pulled apart by fibers Move towards opposite poles of dividing cells

12. Telophase Chromosomes in opposite ends Spindle fibers break down Nuclear envelope reforms Nucleolus in each cell Cytokinesis

13. MOVIE

14. Homework PQRST 154-159 Due Wednesday Cover Page Due Tomorrow Notebook Check Tomorrow –Order online