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Understanding Cell Division: Mitosis and Meiosis

Explore the forms of DNA, the reasons behind cell division, types of division, and phases of mitosis and meiosis. Learn how cells divide and their significance in growth, repair, and reproduction.

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Understanding Cell Division: Mitosis and Meiosis

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  1. CELL DIVISION mitosis & meiosis

  2. Forms of DNA • When the cell is NOT dividing = chromatin • When the cell IS dividing = chromosome Monovalent chromosome Bivalent chromosome

  3. Why do cells divide? • Replacement - cells wear out & die • Repair - tissues can be damaged by injury or infection • Growth of the organism • Reproduction

  4. Types of cell division • Mitosis • New cells are identical to the old cells • Chromosome number is the same in parent & daughter cells (diploid -2n) • Growth, repair, & asexual reproduction

  5. MITOSIS

  6. Meiosis • Parent cell divides twice to produce 4 cells • Produces gametes (sex cells –sperm/eggs) • Daughter cells have half the original number of chromosomes (haploid -1n)

  7. 4.When two gametes join to form a zygote, it will have the normal # of chromosomes

  8. MEIOSIS

  9. 5. Daughter cells are not Genetically identical • a.) Homologous chromosomes separate, sending one version of each to the new cells. • b.) Crossing –Over: sometimes chromosomal segements are exchanged between Homologous Chromosomes.

  10. Phases of Mitosis • Interphase • Growth & normal cell activities • DNA = chromatin *as the cell prepares for division, DNA is duplicated

  11. Prophase • Chromatin thickens & reveals duplicated chromosomes (bivalent) • Centrioles move to poles • Nuclear membrane dissolves

  12. Metaphase • Bivalent chromosomes line up along equator of cell • Chromosomes attach to spindle fibers

  13. Anaphase • Spindle fibers pull monovalent chromosomes to opposite ends of cell **an identical set of chromosomes moves to each pole

  14. Telophase • Chromosomes uncoil & become chromatin again – Nuc. Memb Reforms • Cytokinesis: cell membrane pinches in to form 2 separate cells

  15. Phases of Meiosis • Cells go through two rounds of division during meiosis, resulting in 4 haploid cells

  16. Meiosis I & II Section 11-4 Diff. genes Same genes

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