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Reviewing Mitosis

Reviewing Mitosis. Comparing Plant & Animal Cells. Animal Cells Have centrioles! Cytokinesis simple pinching of cell membranes. Plant Cells No centrioles Equatorial plate Cytokinesis must form 2 membranes PLUS 2 cell walls. Animal vs. Plant Mitosis. Meiosis. Formation of Gametes.

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Reviewing Mitosis

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  1. Reviewing Mitosis Comparing Plant & Animal Cells

  2. Animal Cells Have centrioles! Cytokinesis simple pinching of cell membranes Plant Cells No centrioles Equatorial plate Cytokinesis must form 2 membranes PLUS 2 cell walls Animal vs. Plant Mitosis

  3. Meiosis Formation of Gametes

  4. Definitions • Gamete • Sperm • Ovum (plural ova) • Testes • Ovaries • Zygote • Fertilization • Haploid • Diploid

  5. Meiosis • Two nuclear divisions • Creates haploid gametes • In animals, sperm and ova • In plants, spores • Crossing Over occurs • 4 daughter cells are created.

  6. Meiosis Leads to Genetic Recombination!!!

  7. Meiosis I: Separation of Homologues • Prophase I • Chromosomes Condense • Nuclear Envelope Disappears • Spindle Formed (Asters seen here) • Homologues Pair Up • Crossing-over occurs here!

  8. Metaphase I • Homologous chromosomes move to equator

  9. Anaphase I • Homologues separate • Chromatids do not separate from centromeres!

  10. Telophase I • Nuclear envelope usually does not reform. • Chromosome number in 2 new cells is now half because chromatids did not separate. • THIS IS REDUCTION DIVISION! • Cytokinesis may or may not occur.

  11. Meiosis II • No replication of chromosomes!!!! • Proceeds just like mitosis • Starts and ends with haploid cells

  12. Ovum Formation • Meiotic stages are the same • One daughter cell keeps ALL of the cytoplasm • Other 3 daughter cells only have genetic material – Polar Bodies (Barr Bodies)

  13. Sperm Formation • Cytoplasm and Nuclear Material Divides evenly. • Flagella are added last to the cells following differentiation • Define “differentiation” in your notes here.

  14. Draw a sperm and egg uniting to form a zygote. Be sure to include the number of chromosomes for each.

  15. Using 2 different colored pencils, draw two homologous chromosomes before and after they cross over.

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