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Lab 9b: Meiosis

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. Chromosomes.

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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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