1. © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e1 There is a Need for Cell Division During development  For the fertilized egg to divide into a multicellular organism In adults  To repair damage, and replace worn out cells  And is needed in reproduction

2. © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e2 Review The Eukaryotic Cell Cycle G 0 Phase G 1 Phase S Phase G 2 Phase Division Mitosis and cytokinesis Daughter Cells

3. © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e3 Mitosis & Cytokinesis InterphaseMitosis Prophase (late Prophase)MetaphaseAnaphaseTelophase and cytokinesis

4. © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e4 Term: Homologous Chromosomes 46 chromosomes are arranged in 23 pairs  One came from each parent  Talking only about humans 22 pairs are autosomes  Both chromosomes are homologs 1 pair are sex chromosomes  XX -females XY -males (~homologs)

5. © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e5 Meiosis Used to make gametes  Eggs and sperm Chromosome number is halved (haploid) Zygote is diploid after fertilization Meiosis Fertilization Mitosis 2n n

6. © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e6 Meiosis I vs. Mitosis ProphaseMetaphaseAnaphaseTelophase and cytokinesis ProphaseMetaphaseAnaphaseTelophase and cytokinesis Mitosis Meiosis Sister Chromatids separate Sister Chromatids remain attached

7. © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e7 Meiosis II Metaphase II Anaphase II Telophase II & Cytokinesis

8. © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e8 Meiosis insures that A. Each gamete receives the same genes B. Chromosome number is doubled in the gametes C. Zygotes produced by fertilization have the normal number of chromosomes D. All paternal chromosomes end up in the same gamete Concept Quiz

9. © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e9 Process Animation 9.1 The Cell Division Cycle  Macintosh Macintosh  Windows Windows

10. © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e10 Process Animation 9.2 Mitosis and Cell Division  Macintosh Macintosh  Windows Windows

11. © 2006 W.W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e11 Process Animation 9.3 Meiosis  Macintosh Macintosh  Windows Windows