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Meiosis

Meiosis. Division of Sex Cells. Meiosis. A process of cell division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell; formation of gametes Diploid – 2 sets of chromosomes (2 copies of each)

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Meiosis

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  1. Meiosis Division of Sex Cells

  2. Meiosis • A process of cell division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell; formation of gametes • Diploid – 2 sets of chromosomes (2 copies of each) • Haploid – 1 set of chromosomes (1 copy of each) • Homologous – chromosomes that each have a corresponding chromosome from the opposite sex parent (1 from father, 1 from mother)

  3. Meiosis Stages • Meiosis usually involves 2 distinct stages • Meiosis I • Meiosis II

  4. Prophase I (Meiosis I) • Each chromosome pairs with its corresponding homologous chromosome to form a tetrad. • There are 4 chromatids in a tetrad. • Crossing-over may occur here • Crossing-over is when chromosomes overlap and exchange portions of their chromatids.

  5. Prophase I

  6. Metaphase I • Spindle fibers attach to the chromosomes • Chromosomes line up in the middle of the cell

  7. Metaphase I

  8. Anaphase I • The fibers pull the homologous chromosomes toward opposite ends of the cell.

  9. Anaphase I

  10. Telophase I & Cytokinesis • Nuclear membranes form. • The cell separates into 2 cells.

  11. Telophase I

  12. Prophase II (Meiosis II) • Meiosis I results in two haploid (N) cells. • Each cell has half the number of chromosomes as the original cell.

  13. Prophase II

  14. Metaphase II • The chromosomes line up similar to metaphase in mitosis.

  15. Metaphase II

  16. Anaphase II • Sister chromatids separate and move to opposite ends of the cell.

  17. Anaphase II

  18. Telophase II • Meiosis II results in 4 haploid cells.

  19. Telophase II

  20. Gamete Formation • In males, meiosis results in 4 sperm cells • In females, meiosis results in 1 egg cell and three polar bodies, which are not used in reproduction.

  21. Mitosis vs Meiosis

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