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Download Biology 162 Discussion Section Week 7 The Chromosome Dance
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Biology 162 Discussion Section Week 7 The Chromosome Dance Chapters 12 & 13 (the Cell Cycle; Meiosis and Sexual Life Cycles) are challenging ones. They describe a process of fundamental significance to life, cell division, but they are filled with so much factual information that it is easy for the important principles to be obscured. Unfortunately, a full appreciation of cell division is not possible without a thorough understanding of the mechanisms underlying mitosis and meiosis. Mitosis is the process of cell division responsible for growth, development, tissue turnover, and tissue repair in multicellular organisms. Meiosis, which involves two successive steps of cell division (meiosis I and meiosis II), is central to gamete formation in sexually reproducing organisms. Your GSI will help you to understand these processes and the differences between them by leading you through “the Chromosome Dance”. Before you begin, be sure you can define (and fully understand!) the following terms: haploid vs. diploidhomologous chromosomes vs. sister chromatidsThen, jot down the sequence of events occurring in Mitosis & Meiosis Mitosis Meiosis I Meiosis II Questions for Discussion 1. Fill in the table below. When you can do so without referring to the text, your knowledge of cell division is sufficient for you to consider the larger issue of the significance of mitosis and meiosis to multicellular organisms. Mitosis Meiosis I Meiosis II Generates two diploid cells from a diploid cell Generates two haploid cells from a diploid cell Generates two haploid cells from a haploid cell Homologous chromosomes separate during anaphase Sister chromatids separate during anaphase Sister chromatids are not necessarily identical Sister chromatids are identical DNA replicates prior to prophase DNA does not replicate prior to prophase Crossing over can occur Non-disjunction can occur Centromeres divide Individual chromosomes align at equatorial plate during metaphase Homologous pairs of chromosomes align at equatorial plate during metaphase Occurs in somatic cells Occurs in sex cells Produces two daughter cells that are genetically identical to each other and to the parent cell Produces two daughter cells that are not genetically identical to each other and to the parent cell 2. The crucial difference between mitosis and meiosis is encapsulated nicely by the statement that “mitosis is a mechanism for constancy,” whereas “meiosis is a mechanism for diversity.” Why is it important that organisms have one process of cell division that ensures “constancy” and another that ensures “diversity”? 3. Does chance play a role in either mitosis or meiosis? If so, in what steps or processes?
