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G during the g1 phase a cell prepares to divide the

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Unformatted text preview: ide The cell reaches a restriction point and is The restriction committed on a pathway to cell division committed Then the cell advances to the S phase, where Then chromosomes are replicated chromosomes The two copies of a replicated chromosome are The termed chromatids chromatids They are joined at the centromere to form a pair of They sister chromatids sister During the G2 phase, the cell accumulates the materials that are necessary for nuclear and cell division cell It then progresses into the M phase of the cycle It where mitosis occurs mitosis Mitosis is subdivided into five phases Prophase Prometaphase Metaphase Anaphase Telophase Chromosomes are Chromosomes decondensed decondensed By the end of this By phase, the chromosomes have already replicated already The centrosome The divides divides Nuclear envelope Nuclear dissociates into smaller vesicles vesicles Centrosomes separate Centrosomes to opposite poles to The mitotic spindle The apparatus is formed apparatus Composed of Composed mircotubules (MTs) mircotubules Microtubules are formed by rapid polymerization of tubulin Microtubules proteins proteins There are three types of spindle microtubules 1. Aster microtubules Important for positioning of the spindle apparatus 2. Polar microtubules Help to “push” the poles away from each other 3. Kinetochore microtubules Attach to the kinetochore , which is bound to the centromere Attach kinetochore of each individual chromosome of Spindle fibers interact with Spindle the sister chromatids the Kinetochore microtubules Kinetochore grow from the two poles grow If they make contact with If a kinetochore, the sister chromatid is “captured” chromatid If not, the microtubule If depolymerizes and retracts to the centrosome retracts The two kinetochores on a The pair of sister chromatids are attached to kinetochore MTs on opposite poles on Pairs of sister chromatids Pairs align themselves along a plane called the metaphase plate plate Each pair of chromatids is Each attached to both poles by kinetochore microtubules kinetochore The connection holding The the sister chromatids together is broken together Each chromatid, now an Each individual chromosome, is linked to only one pole pole As anaphase proceeds Kinetochore MTs Kinetochore shorten shorten Chromosomes move to Chromosomes opposite poles opposite Polar MTs lengthen Poles themselves move Poles further away from each other other Chromosomes reach their respective Chromosomes poles and decondense pole...
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