1. AP Biology 2005-2006 The Cell Cycle: Cell Growth, Cell Division, Mitosis & Meiosis

2. AP Biology 2005-2006 Where it all began…  You started as a cell smaller than a period at the end of a sentence….

3. AP Biology 2005-2006 Getting from there to here…  Cell division  continuity of life = reproduction of cells  reproduction  unicellular organisms  growth  repair & renew  Cell cycle  life of a cell from origin to division into 2 new daughter cells

4. AP Biology 2005-2006 Getting the right stuff  What is passed to daughter cells?  exact copy of genetic material = DNA  this division step = mitosis  assortment of organelles & cytoplasm  this division step = cytokinesis

5. AP Biology 2005-2006 Copying DNA  Dividing cell duplicates DNA  separates each copy to opposite ends of cell  splits into 2 daughter cells  human cell duplicates ~3 meters DNA  separates 2 copies so each daughter cell has complete identical copy

6. AP Biology 2005-2006 Cell cycle  Cell has a “life cycle” cell is formed from a mitotic division cell grows & matures to divide again cell grows & matures to never divide again G 1, S, G 2, MG0G0 epithelial cells, blood cells, stem cells brain nerve cells liver cells

7. AP Biology 2005-2006 Cell Division cycle  Phases of a dividing cell’s life  interphase  cell grows  replicates chromosomes  produces new organelles  mitotic phase  cell separates & divides chromosomes  mitosis  cell divides cytoplasm & organelles  cytokinesis

8. AP Biology 2005-2006 Interphase  90% of cell life cycle  Characteristics  nucleus well-defined  DNA loosely packed in long chromatin fibers

9. AP Biology 2005-2006 Mitosis  copying cell’s DNA & dividing it between 2 daughter nuclei  Mitosis is divided into 4 phases  prophase  metaphase  anaphase  telophase

10. AP Biology 2005-2006 Prophase  DNA condenses  visible as chromosomes  Centrioles move to opposite poles of cell  Spindle forms  Nucleolus disappears  Nuclear membrane breaks down

11. AP Biology 2005-2006 Metaphase  Chromosomes align along the middle of cell  meta = middle  helps to ensure chromosomes separate properly  so each new nucleus receives only 1 copy of each chromosome

12. AP Biology 2005-2006 Anaphase  Sister chromatids separate  move to opposite poles  Poles move farther apart

13. AP Biology 2005-2006 Telophase  Chromosomes arrive at opposite poles  nuclei form  nucleoli form  chromosomes disperse  Cytokinesis begins  cell division

14. AP Biology 2005-2006 Cytokinesis  Animals  Cleavage occurs  The cytoplasm is beginning to divide in half

15. AP Biology 2005-2006 Cytokinesis in Animals

16. AP Biology 2005-2006 Mitosis in whitefish blastula

17. AP Biology 2005-2006 onion root tip

18. AP Biology 2005-2006 How about the rest of us?  What if a complex multicellular organism (like us) wants to reproduce?  joining of egg + sperm  Do we make egg & sperm by mitosis? 46 + 92 eggspermzygote

19. AP Biology 2005-2006 How do we make sperm & eggs?  reduce 46 chromosomes  23 chromosomes  half the number of chromosomes 23 46 egg sperm 46 meiosis 46 fertilization 23

20. AP Biology 2005-2006 Meiosis = reduction division  Meiosis  special cell division in sexually reproducing organisms  reduce 2n  1n  diploid  haploid  half  makes gametes  sperm, eggs

21. AP Biology 2005-2006 2nd division of meiosis separates sister chromatids 1st division of meiosis separates homologous pairs Double division of meiosis DNA replication

22. AP Biology 2005-2006 Mitosis vs. Meiosis  Mitosis  1 division  daughter cells genetically identical to parent cell  produces 2 cells  2n  2n  produces cells for growth & repair  no crossing over  Meiosis  2 divisions  daughter cells genetically different from parent  produces 4 cells  2n  1n  produces gametes  crossing over

23. AP Biology 2005-2006 Crossing over  During Prophase 1  homologous pairs swap pieces of chromosome  sister chromatids intertwine  crossing over tetrad