Test_CellCycle - Cell Division Results in Genetically...

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Cell Division Results in Genetically Identical Daughter Cells : A dividing cell duplicates its DNA, allocates the two copies to opposite ends of the cell, and only then splits into daughter cells. Eukaryotic chromosomes are made of chromatin - Chromatin = complex of DNA + associated protein molecules When a cell isn’t dividing (or when its DNA is replicating),chromosomes are chromatin fibers Each duplicated chromosome has 2 sister chromatids - Initially attached lengthwise by cohesins (protein complexes) - Centromere = Specialized region where the 2 chromatids are most closely attached, visible when chromosomes condense - Once chromatids separate, they are considered individual chromosomes Mitosis is immediately followed by cytokinesis - Mitosis = Division of nucleus - Cytokinesis = Division of the cytoplasm Meiosis = variation of cell division that yields non-identical daughter cells that have only one set of chromosomes The Mitotic Phase Alternates with Interphase in the Cell Cycle : Walther Flemming (1882) – Developed dyes that allowed him to observe the behavior of chromosomes during mitosis and cytokinesis Mitotic Phase (M Phase) – Shortest part of cell cycle; Includes mitosis and cytokinesis Interphase – 90% of the cell cycle; when cell grows & copies its chromosomes in preparation for cell divison During all the subphases, the cell grows by producing proteins and cytoplasmic organelles (mitochondria, ER, etc) - Chromosomes duplicated only during S phase Stages of mitosis: Prophase, prometaphase, metaphase, anaphase, telophase (cytokinesis overlaps with anaphase/telophase) Diagram pages 232- 233 - G2 of Interphase: *Nuclear envelop bounds nucleus *Nucleus contains one or more nucleoli *2 centrosomes have formed by replication of 1 *In animal cells, each centrosome has 2 centrioles *Chromosomes replicated during S phase can’t be seen yet b/c they haven’t condensed - Prophase: *Chromatin becomes tightly coiled (chromosomes condense) *Nucleoli disappear *Duplicated chromosomes appear as 2 sister chromatids joined at centromeres and along their arms by cohesins *Mitotic spindle begins to form (composed of centrosomes & MT that extend from them, array of shorter MT that extend centrosomes are called asters) *Centrosomes move away from each other, propelled by lengthening MT b/w them - Prometaphase: *Nuclear envelope fragments
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Test_CellCycle - Cell Division Results in Genetically...

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