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Quick review: identify this stage of the diploid cell cycle.

Quick review: identify this stage of the diploid cell cycle. Prophase. Quick review: identify this stage of the diploid cell cycle. telophase. Quick review: identify this stage of the diploid cell cycle. anaphase. Quick review: identify this stage of the diploid cell cycle. Prophase.

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Quick review: identify this stage of the diploid cell cycle.

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  1. Quick review: identify this stage of the diploid cell cycle. Prophase

  2. Quick review: identify this stage of the diploid cell cycle. telophase

  3. Quick review: identify this stage of the diploid cell cycle. anaphase

  4. Quick review: identify this stage of the diploid cell cycle. Prophase

  5. Quick review: identify this stage of the diploid cell cycle. metaphase

  6. Quick review: identify this stage of the diploid cell cycle. interphase

  7. Meiosis

  8. Meiosis • Defined: Process where the chromosome number is reduced by half • Gametes created (egg, sperm, pollen) • End Result: Four Haploid Cells

  9. Interphase • Same process • G1: Growth, organelle replication, normal functions • S: Chromatin duplicated • G2: Growth and normal functions

  10. Synthesis (S stage) Chromatin duplicated

  11. Prophase 1 Mom 1 • Similar to mitosis, except… • Two Events: • 1) Synapsis: Pairing of homologous chromosomes • Dad’s #1 chromosome pairs with Mom’s #1, etc… • The four paired chromatids equals a TETRAD • 2) Crossing Over: Exchange of genes Dad 1

  12. Early Prophase 2 Chromosomes form 1 3 2 Nucleus dissolves 3 1

  13. Synapsis tetrad tetrad 2 Spindle fibers pull homologous chromosomes together 1 3 2 3 1 tetrad

  14. Metaphase 1 • Homologous chromosomes (tetrads) align along cell equator 2 2 1 1 3 3

  15. Anaphase 1 • Homologous chromosomes are pulled apart • Tetrads separated 1 1 3 3 2 2

  16. Telophase 1 • Cytokinesis divides the cells • Not apart of telophase • Each cell contains 1 of the homologous chromosomes • In humans = 23 chromosomes 1 1 3 3 2 2

  17. Let’s review…starting with the S stage Chromatin duplicated

  18. Prophase 1 2 Chromosomes form 1 3 2 Nucleus dissolves 3 1

  19. Prophase 1 (Synapsis) tetrad tetrad 2 Spindle fibers pull homologous chromosomes together 1 3 2 3 1 tetrad

  20. Metaphase 1 2 2 1 1 3 3 Tetrads pulled to middle of cell

  21. Anaphase 1 1 1 3 3 2 2 Tetrads pulled apart… one entire chromosome to each end of the cell

  22. Telophase 1 1 1 3 3 2 2 Nucleus reforms… Cell Plate forms Cytokinesissplits the cell into two…

  23. Prophase 2 • Same as mitosis • Note: No new DNA was created (no 2nd interphase) 1 1 3 3 2 2

  24. Metaphase 2 • Remaining chromosomes are aligned at cell equator 1 1 3 3 2 2

  25. Anaphase 2 • Chromatids are pulled to opposite ends

  26. Telophase 2 • Nucleus reforms on the four new cells • Cell plate forms • Cytokinesis divides the cells • Not apart of telophase • Chromatids uncoil • End Result: Four haploid cells

  27. Spermatogonium (diploid) Spermatogenesis Meiosis 1 • Defined: Production of sperm cells • Location: male testes • Makes final changes to sperm cell • Four haploid sperm cells at a time Meiosis 2 Spermatogenesis

  28. Oocyte (diploid) Oogenesis Meiosis 1 • Defined: Production of the egg cell (ovum) • Location: female ovaries • During meiosis I: Cytoplasm distributed unequally • During meiosis II:cells split again • End result: 1 mature cell, 3 polar bodies Meiosis 2 Oogenesis

  29. Division of somatic cells Ex: Blood cells, skin cells, nerve cells… End Result: 2 Diploid Cells Importance: Replaces aging cells Importance: Form of asexual reproduction Division of gametes Ex: Sperm and Egg cells End Result: 4 Haploid cells Importance: Reduces the gamete chromosome number by half Mitosis Meiosis

  30. Let’s review…starting with the S stage Chromatin duplicated

  31. Prophase 1 2 Chromosomes form 1 3 2 Nucleus dissolves 3 1

  32. Prophase 1 (Synapsis) tetrad tetrad 2 Spindle fibers pull homologous chromosomes together 1 3 2 3 1 tetrad

  33. Metaphase 1 2 2 1 1 3 3 Tetrads pulled to middle of cell

  34. Anaphase 1 1 1 3 3 2 2 Tetrads pulled apart… one entire chromosome to each end of the cell

  35. Telophase 1 1 1 3 3 2 2 Cytokinesis splits the cell into two… Nucleus reforms

  36. Prophase 2 1 1 3 3 2 2 Nucleus dissolves…. Spindle fibers form

  37. Metaphase 2 1 1 3 3 2 2 Chromosomes are pulled to middle of each cell

  38. Anaphase 2 Chromosomes split apart… One chromatid pulled to each end of the cell

  39. Telophase 2 Nucleus reforms… cell plate created Cytokinesissplits the two cells into four cells… Chromatidsunwind into chromatin

  40. REVIEW 1) Name three ways that meiosis and mitosis differ. 2) Pick a stage of meiosis…any stage. Describe what happens in it. 3) What type of cells does meiosis create? 4) What are homologous chromosomes? 5) When do homologous chromosomes move to opposite ends of the cell? 6) When do chromatids move to opposite ends of the cell? 7) Why is no DNA created in meiosis 2? 8) How does meiosis differ in males vs. females?

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