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Meiosis

Meiosis. Division of Sex Cells. Meiosis. A process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell. Diploid – 2 sets of chromosomes Haploid – 1 set of chromosomes

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Meiosis

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  1. Meiosis Division of Sex Cells

  2. Meiosis • A process of reduction division in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell. • Diploid – 2 sets of chromosomes • Haploid – 1 set of chromosomes • Homologous – chromosomes that each have a corresponding chromosome from the opposite sex parent

  3. Meiosis

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

  5. Prophase I • Each chromosome pairs with its corresponding homologous chromosome to form a tetrad. • There are 4 chromosomes in a tetrad. • The pairing of homologous chromosomes is the key to understanding meiosis. • Crossing-over may occur here • Crossing-over is when chromosomes overlap and exchange portions of their chromatids.

  6. Prophase I

  7. Metaphase I • Spindle fibers attach to the chromosomes

  8. Metaphase I

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

  10. Anaphase I

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

  12. Telophase I

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

  14. Prophase II

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

  16. Metaphase II

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

  18. Anaphase II

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

  20. Telophase II

  21. 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.

  22. Mitosis vs Meiosis

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