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Mitosis and Meiosis

BSC 1005L. Mitosis and Meiosis. Why do eukaryotic cells divide?. Growth and Repair Mitosis Produces 2 identical cells with same # chromosomes (diploid #) Reproduction Meiosis Produces cells with ½ chromosomes (haploid #). Eukaryotic Cell Cycle. 2 main phases Mitosis Interphase

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Mitosis and Meiosis

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  1. BSC 1005L Mitosis and Meiosis

  2. Why do eukaryotic cells divide? • Growth and Repair • Mitosis • Produces 2 identical cells with same # chromosomes (diploid #) • Reproduction • Meiosis • Produces cells with ½ chromosomes (haploid #)

  3. Eukaryotic Cell Cycle • 2 main phases • Mitosis • Interphase • Long period between cell division • Some cells stay in interphase indefinitely G1 is where the cell performs it’s “normal” cell functions (may be days or years depending on cell type)

  4. Ploidy • # of sets of chromosomes in a cell • Haploid (n) – one set • Egg and sperm • Diploid (2n) – two sets • All of our other cells • Example: • In humans, • Haploid # = 23 • Diploid # = 46 • These #’s will vary depending on the species!!!!!!

  5. Onion Root Tip – MitosisArea of lots of cells undergoing mitosis in various stages What you will see at 40x – Have to magnify further to See individual cells

  6. Onion Root Tip - mitosis

  7. Meiosis • Humans have 46 chromosomes, 23 homologous pairs • What is homologous? • During Meiosis, it is VERY important that one of EACH homologous pair ends up in the gamete (sperm or egg) • Why?

  8. Gametogenesis in Animals • Spermatogenesis • Oogenesis • Notice how there is 1 egg

  9. Onion Root Tip - Mitosis

  10. Whitefish blastula - Mitosis What you will see at 40x, each circle is a Cross-section of the blastula, focus in to see individual cells Focus in on the individual cells This is an example of anaphase

  11. Differences between mitosis and meiosis • Mitosis is one division, meiosis is two (meiosis I and II) • Mitosis results in 2 identical daughter cells, meiosis results in 4 haploid cells • Homologous chromosomes find each other before meiosis I • Crossing over occurs • Mitosis is for growth and repair, meiosis is for reproduction

  12. In this lab: • Observe microscope slides of mitosis and meiosis • Look at models of mitosis and meiosis • Tutorials of these models can be found on the Biology Department Laboratory resources page • http://faculty.irsc.edu/DEPT/BiologicalSciences/mit%20mei%20modelsHTML/index.htm • Use bead models to demonstrate mitosis and meiosis

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