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Understanding Meiosis: The Key Concepts and Processes Explained

Learn how meiosis reduces chromosome number, creates genetic diversity, and differs from mitosis. Explore the two cell divisions, homologous chromosomes, gametogenesis, and crossing over. Helpful animations included.

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Understanding Meiosis: The Key Concepts and Processes Explained

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  1. KEY CONCEPT During meiosis, diploid cells undergo two cell divisions that result in haploid cells.

  2. Cells go through two rounds of division in meiosis. • Meiosis reduces chromosome number and creates genetic diversity.

  3. Process of Meiosis: 2 cell divisions, 2 parts: Meiosis I and Meiosis II Homologous chromosomes Sister chromatids Attached together at the centromere Are duplicates of each other (same information) Separate in Meiosis II • Inherit 1 from each parent • Carry the same or similar information • Separate in Meiosis I homologouschromosomes sister chromatids

  4. Meiosis I occurs after DNA has been replicated. • Meiosis I divides homologous chromosomes in four phases.

  5. Meiosis II divides sister chromatids in four phases. • DNA is not replicated between meiosis I andmeiosis II.

  6. Meiosis animations • http://www.stolaf.edu/people/giannini/flashanimat/celldivision/meiosis.swf • https://www.youtube.com/watch?v=vA8aMpHwYh0Meiosis animations

  7. Meiosis differs from mitosis in significant ways. • Meiosis has two cell divisions while mitosis has one. • In mitosis, homologous chromosomes never pair up. • Meiosis results in haploid cells; mitosis results in diploid cells.

  8. Haploid cells develop into mature gametes. • Gametogenesis is the production of gametes. • Gametogenesis differs between females and males. • Sperm become streamlined and motile. • Sperm primarily contribute DNA to an embryo. • Eggs contribute DNA, cytoplasm, and organelles to an embryo. • During meiosis, the egg gets most of the contents; the other cells form polar bodies.

  9. Crossing Over (Also in Section 6.6) • Often occurs in Prophase I of meiosis • Homologous chromosome pairs are together on one spindle fiber • Called synapsis • Portions of chromosome segments are exchanged • Produces more genetic diversity

  10. Meiosis and crossing over • https://www.youtube.com/watch?v=5x_Rp1mwotQ

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