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Lab 9b: Meiosis

Learn about the process of meiosis and how it produces haploid cells essential for gamete formation. Explore the stages of meiosis, from prophase to cytokinesis, and understand the differences from mitosis. Engage in modeling activities to grasp the intricacies of meiosis and complete study guide questions for a comprehensive understanding.

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Lab 9b: Meiosis

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  1. Lab 9b: Meiosis • Prelab 9 and Informal Lab Report is due. • Microworlds are due NEXT CLASS! • You should have time to work on it today. • Turn in all 10 Microworlds including the 4 that have been graded. • You may use mitosis & meiosis slides for this.

  2. Chromosomes

  3. Mitosis makes cells, but what about making babies? • Does Mitosis produce gametes (sex cells: egg and sperm)?

  4. Meiosis • Resembles 2 rounds of mitosis • 2 cell divisions (meiosis I and meiosis II) • 4 resulting haploid cells HAPLOID= 1 copy DIPLOID = 2 copies

  5. Meiosis Haploid gametes (n = 23) n Egg cell n Sperm cell Meiosis Fertilization A Meiosis video in a nematode. A little slow downloading but only 24 sec. Diploid zygote (2n = 46) 2n Multicellular diploid adults (2n = 46) Mitosis and development

  6. Meiosis I: Prophase I • Chromosomes condense • Nuclear membrane degrades • Centrioles (Spindle fibers) move to opposite poles • Homologous chromosomes (homologues) pair up • Crossing over occurs

  7. Meiosis I: Metaphase I • Spindle fibers attach to centromeres • Paired Homologues line up on equator (metaphase plate)

  8. Meiosis I: Anaphase I • Homologues separate (each still consists of two sister chromatids) • Chromosome # halves (counting centromeres) • Cells destined to be haploid

  9. Meiosis I: Telophase I • Nuclear membranes reforms • Cytokinesis follows • Haploid cells as the homologs split not the sister chromatids

  10. Meiosis II: Prophase II • Chromosomes condense again • Nuclear membrane breaks down • 2 sister chromatids to 1 chromosome

  11. Meiosis II: Metaphase II • Spindle fibers attach to centromeres • Chromosomes line up on the metaphase plate

  12. Meiosis II: Anaphase II • Sister chromatids separate and move to opposite plates • The microtubules contract, moving the chromatids

  13. Meiosis II: Telophase II • Nuclear membranes reforms • Chromosomes unwrap • Cytokinesis follows • 4 haploid cells produced (at least in males, oogenesis is more complicated)

  14. Ex. 1: Modeling Meiosis • Use either Play-doh or the Pop Beads to model meiosis • Make a diploid cell with 3 chromosomes of different sizes. • Be sure to model all the steps in meiosis • One of the exercises models crossing over • Important, answer the Study Guide Questions at the end of the lab. It compares mitosis and meiosis.

  15. Rest of Lab • When finished, your table group needs to walk me through the steps of meiosis w/o using notes or the manual! • If I pass you, turn in a list of your names. • Work on your Microworlds project, due next week. (Micoworld slides, pond water, mitosis/meiosis slides available.) • When you are all done, you are free to go!

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