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Cell Division

Cell Division. Making New Cells. Cell Division. Cells come from pre-existing cells… Cells need to reproduce! Single-celled organisms -- asexual reproduction. Multi-celled organisms – growth. Cell Division = Cytokinesis Nuclear Division = Karyokinesis. Prokaryotes – Binary Fission.

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Cell Division

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  1. Cell Division Making New Cells

  2. Cell Division • Cells come from pre-existing cells… • Cells need to reproduce! • Single-celled organisms -- asexual reproduction. • Multi-celled organisms – growth. • Cell Division = Cytokinesis • Nuclear Division = Karyokinesis

  3. Prokaryotes – Binary Fission • Simple

  4. Eukaryotes – more complex • Chromosomes • Chromosome Structure • Chromatin • Unduplicated • Duplicated • Chromosome Number • Diploid • Somatic cells (body cells) • Haploid • Germ cells (sex cells)

  5. Karyokinesis • Mitosis • Somatic cells (body cells) • “Cloning” of genetic information – exact copies made and distributed to new cells. • Chromosome # is retained (stays the same). • Meiosis • Germ cells (sex cells) • Genetic information is shuffled – new cells are each different. • Chromosome # is cut in half.

  6. Cell Cycle

  7. Chromosome Duplication • During S-phase = “Synthesis” • Why?.... • So that later, the sister chromatids can separate into different (new) cells!

  8. Mitosis • Prophase • Metaphase • Anaphase • Telophase

  9. Prophase • Nuclear Envelope Disappears • Nucleolus Disappears • Chromosomes Condense • Chromatin Chromosomes • Spindle Fibers (Microtubules) • Attach to Centromeres • Attach to M.T.O.C.s

  10. Metaphase • Chromosomes line up on the ‘Metaphase Plate’ • pushed & pulled by the spindle fibers • Spindle Apparatus well developed.

  11. Anaphase • Chromosomes each broken at their centromeres • spindle fibers on each side shorten • New (unduplicated) chromosomes move toward the M.T.O.C.s

  12. Telophase • Chromosomes stop moving when they reach the spindle poles (at the M.T.O.C.s) • Nuclear Envelope re-forms (2x) • Nucleolus re-forms (2x) • Spindle fibers disappear • Cytokinesis

  13. Cytokinesis Cleavage Furrow divides the cells Cell Plate divides the cells

  14. Meiosis • Associated with Sex! • Sexual Reproduction involves • 2 parents • Mixing of genetic information • Life cycles, with MEIOSIS & FERTILIZATION

  15. Life Cycles HAPLOID GAMETIC DIPLOID

  16. Meiosis • Mixing of Genetic Information • Germ Cells (Sex Cells) • Reduction in Chromosome Number • Diploid  Haploid • 2 Divisions • Meiosis I --- P,M,A,T • Meiosis II --- P,M,A,T • Results in 4 cells

  17. Meiosis I • Prophase I • Metaphase I • Anaphase I • Telophase I • Pairing and separation of Homologous Chromosomes • Crossing Over • Independent Assortment • 2n1n VARIATION!

  18. Meiosis I

  19. Meiosis II • Prophase II • Metaphase II • Anaphase II • Telophase II • Separation of sister chromatids • 1n1n • Results in 4 DIFFERENT cells.

  20. Meiosis II

  21. MEIOSIS -- Spermatogenesis

  22. MEIOSIS -- Oogenesis Stimulated by Fertilization

  23. MITOSIS vs MEIOSIS

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