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Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
Meiosis Lecture
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Meiosis Lecture

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Meiosis lecture for CHS IB Biology HL Year 1

Meiosis lecture for CHS IB Biology HL Year 1

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  • 1. Meiotic Cell Division
  • 2.
    • Sexual reproduction is the most common way for eukaryotic organisms to produce offspring
    • Parents make gametes with half the amount of genetic material ( haploid )
    • These gametes fuse with each other during fertilization to generate a new organism
    Sexual Reproduction
  • 3.
    • Most eukaryotic species are heterogamous
      • These produce gametes that are morphologically different
        • Sperm cells
          • Relatively small and mobile
        • Oocytes or ova
          • Usually large and nonmobile
          • Store large amounts of nutrients
        • Microspores (Pollen)
        • Macrospores (Ovules)
    Gametes
  • 4. How Does One Make a Haploid Gamete?
    • Answer – meiosis
    • Haploid cells are produced from diploid cells during gametogenesis
    • The chromosomes must be distributed to reduce the chromosome number to half its original value
    • but simultaneously sorted to assure that each chromosome (& its genes) is represented in each gamete
  • 5. Mitosis vs Meiosis
    • Produces two diploid daughter cells
    • Produces daughter cells that ARE genetically identical
    • Produce four haploid daughter cells
    • Produces daughter cells that are NOT genetically identical
  • 6.
    • Meiosis begins after a cell has progressed through G 1 , S, & G 2
    • Meiosis involves two successive divisions
      • Meiosis I and II
      • Each of these is subdivided into
        • Prophase
        • Metaphase
        • Anaphase
        • Telophase
    Meiosis
  • 7. Periods of Prophase I A physical exchange of chromosome pieces A tetrad
  • 8. Stages of Meiosis I Spindle apparatus complete; pairs of chromatids attached to kinetochore microtubules
  • 9.
    • Tetrads are organized along the metaphase plate
    • Homologous p airs of sister chromatids aligned side by side
      • A pair of sister chromatids is linked to one of the poles
      • And the homologous pair is linked to the opposite pole
      • The arrangement is random with regards to the ( blue and red ) homologues
    Figure 3.13
  • 10. Stages of Meiosis I 3-50 Homologous chromosomes separate from each other The centromere remains between sister chromatids
  • 11. Meiosis
    • Telophase I & cytokinesis of meiosis I is followed meiosis II
    • Meiosis I has reduced the number of chromosomes in the daughter cells to the ½ the diploid number
    • However, each homolog is still composed of 2 recombinant sister chromatids
      • The genetic content is still 2n
    • Meiosis II reduces the genetic content to n
  • 12. Stages of Meiosis II 1 of each type of chromosome (n) in each daughter cell (gamete)
  • 13. Separation of Alleles During Meiosis Prophase I Metaphase I Anaphase I Telophase I Meiosis II Haploid cells Heterozygous ( Yy ) cell from a plant with yellow seeds y y y y y y y Y Y Y Y Y Y Y
  • 14. Separation of Alleles During Meiosis Meiosis I Meiosis II or 2 Ry : : Heterozygous diploid cell ( YyRr ) to undergo meiosis y y y y y y y y y Y Y Y Y Y Y Y Y Y R R R r r y r r R R Y R R R R y R r r r r Y r Y y R r R r r 2 rY 2 ry 2 RY
  • 15. Credits
    • Images
    • Campbell, N.A., & Reece, J.B. (2005). Biology (7 th ed.). San Francisco, CA: Pearson

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