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Lab 9: Meiosis

Lab 9: Meiosis. Prelab 9 and the Lab report is due. Lab 8 is due by the end of the class. (You may work on the 1 st part in lab today. Make sure you turn it in or it is late.) Microworlds is due NEXT CLASS – you should have tons of time to work on it today. Chromosomes.

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Lab 9: Meiosis

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  1. Lab 9: Meiosis Prelab 9 and the Lab report is due. Lab 8 is due by the end of the class. (You may work on the 1st part in lab today. Make sure you turn it in or it is late.) Microworlds is due NEXT CLASS – you should have tons of time to work on it today

  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 • Homologous chromosomes (homologues) pair up • Crossing over occurs • Nuclear membrane degrades

  7. Meiosis I: Metaphase I • Spindle fibers attach to centromeres • 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)

  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 • This only looks as shown when viewed from the equator, it looks like a mess when viewed from the poles.

  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, we’ll skip the more complicated oogenesis)

  14. Modeling Meiosis with Play-doh • 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

  15. Rest of Lab • If needed, finish the protein synthesis part of Lab 8. Turn it in before you go. • Work on your Microworlds project, it is due next week. (Slides and pond water available.) • When you are all done, you are free to go!

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