CellBio4 - 1 Mitosis and Mitotic Chromosomes The DNA is...

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Unformatted text preview: 1 Mitosis and Mitotic Chromosomes The DNA is already duplicated; every chromosome, before division, consists of two identical copies of DNA Each copy is called a chromatid and the two chromatids are held together at a specialized region called the centromere One chromatid Second chromatid A Metaphase Chromosome 2 Centromere A Metaphase Chromosome Important Preparations for Mitosis 1) The DNA is duplicated during S phase, so that each chromosome contains 2 identical copies of DNA (2 identical chromatids) 2) The centrosome is duplicated during G2 to make 2 centrosomes (these become the spindle poles) 3 Mitosis Process in which the two identical chromatids of each chromosome are segregated accurately to two different daughter cells The Fve phases: 1) Prophase 2) Prometaphase 3) Metaphase 4) Anaphase 5) Telophase Prophase Important events 1. The cytoskeleton breaks down, the endomembrane system is dispersed, and the cell becomes round (the cytoplasm becomes almost structureless) 2. Inside the nucleus, the chromosomes condense to the mitotic chromosome form 3. The duplicated centrosomes move to opposite sides of the nucleus and become the 2 poles of the mitotic spindle 4 Very Early Prophase A Cell in Prophase Condensing chromosomes 5 Prometaphase The nuclear envelope breaks down (this is the beginning of prometaphase) Kinetochores form at the centromere regions of the chromatids (this is the place where the microtubules attach to the chromosomes) Kinetochores form 6 A kinetochore A Kinetochore and Kinetochore Microtubules Pro-Metaphase Microtubules growing and shortening from the poles Fnd and become attached to the...
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CellBio4 - 1 Mitosis and Mitotic Chromosomes The DNA is...

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