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Metaphase - Phase Chromosomes Chromatids Chromosome...

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Metaphase During metaphase, the chromosomes have moved to the center of the cell (diagram below, photograph above). This line of chromosomes is referred to as the metaphase plate. The structures in the diagram below are referred to as the spindle apparatus . Kinetochore microtubules are attached to the chromosomes. Polar microtubules are not attached to chromosomes but overlap each other. Asters are short microtubules that radiate from the centrosomes. The spindle apparatus can be seen on the drawing of a cell in metaphase below. Metaphase ends when chromosomes split, thus doubling the number of chromosomes. Anaphase When the chromosomes split at the end of metaphase, the chromosome number is doubled. For example, the number of chromosomes and chromatids during each phase in a human cell is:
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Unformatted text preview: Phase # Chromosomes # Chromatids Prophase 46 92 Metaphase 46 92 Anaphase 92 92 Telophase 92 92 Chromosome movement Microtubules lengthen and shorten by the addition or removal of tubulin dimers. Click here for details in the chapter on cells. Kinetochore microtubules shorten in the region of the kinetochore, pulling the chromosomes apart. Polar microtubules push against each other and thus, push the two centrosomes apart. This, in turn, also pulls the chromosomes apart. The chromosomes move toward poles of cell. Cytokinesis (division of the cell) begins in anaphase. A cleavage furrow forms as actin filaments underneath the plasma membrane constrict in a band called the contractile ring. Two cells will be produced as this process continues....
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