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Cell Division

Cell Division. Meiosis. Meiosis occurs in sexual reproduction when a diploid germ cell produces four haploid daughter cells that can mature to become gametes (sperm or egg). from mom. from dad. child. too much!. meiosis reduces genetic content. Meiosis.

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Cell Division

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  1. Cell Division

  2. Meiosis • Meiosis occurs in sexual reproduction when a diploid germ cell produces four haploid daughter cells that can mature to become gametes (sperm or egg).

  3. from mom from dad child too much! meiosis reduces genetic content Meiosis Goal: reduce genetic material by half Why? n (mom) + n (dad) = 2n (offspring) Just right!

  4. Meiosis I Meiosis II Diploid Haploid Haploid Meiosis: 2 part cell division Sister chromatids separate Homologous Chromosomes pairs separate 2n n n Result: one copy of each numbered chromosome in a gamete.

  5. Spindle fibers Nucleus Nuclear envelope Prophase I (early) (diploid) Prophase I (late) (diploid) Metaphase I (diploid) Anaphase I (diploid) Telophase I (diploid) Meiosis I

  6. Prophase I Early Early prophase Chromosomes condense Spindle forms Nuclear envelope breaks apart .

  7. Prophase I Late Late prophase Chromatids pair (synapse) Crossing over occurs between chromatids of the homologous chromosome pair

  8. Metaphase I Homologous chromosome pairs line up on the cell’s equator

  9. Anaphase I Chromosomes separate and move to opposite poles. Sister chromatids remain Attached at their centromeres.

  10. Telophase I Nuclear envelopes reforms Spindle disappears. Cytokinesis divides cell into two

  11. Sister chromatids have carry different genetic information due to crossing over End product of meiosis is Each Sex cell /gamete has : 1 copy of each chromosome 1 copy of each gene segment Meiosis II

  12. Four Non-identical haploid daughter cells Prophase II (haploid) Metaphase II (haploid) Anaphase II (haploid) Telophase II (haploid) Meiosis II

  13. Prophase II Nuclear envelope fragments. Spindle forms.

  14. Metaphase II Chromosomes align along equator of cell.

  15. Anaphase II Sister chromatids separate and move to opposite poles.

  16. Telophase II Nuclear envelope assembles. Chromosomes unravel. Spindle disappears. Cytokinesis divides cell into two.

  17. Results of meiosis • Four haploid cells • One copy of each chromosome • Not the same genes on each chromosome

  18. “Putting It All Together” - Fertilization

  19. What Meiosis is About Meiosis allows the creation of unique individuals through sexual reproduction. Meiosis Video Link

  20. Meiosis Video Link #1 Meiosis Video Link #2 Meiosis Video Link#3

  21. 2 diploid 4 haploid Crossing over between nonsister chromatids Reduction divisiion Increases genetic variability vs. clones Meiosis 1 Homologous chrom separate Meiosis 2 Sister chromatids separate

  22. Meiosis II produces gametes with one copy of each chromosome and thus one copy of each gene.

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