Lecture 21 12

Lecture 21 12 - Lecture 21 12/03/07 Mitosis Mitosis -...

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Lecture 21 12/03/07 Mitosis Mitosis - functions 1.) Evenly segregate chromosomes after duplication in S phase 2.) Create 2 identical daughter cells from one mother cell Stages o Prophase o Prometaphase o Metaphase o Anaphase o Telophase/Cytokinesis Prophase – 1 st step of mitosis, cell comes out of G2 Has two copies of every chromosome Sister chromatids condense Sister chromatids attached via cohesin Microtubules depolymerize and mitotic spindle starts to form Specifically: 1.) Chromosomes start to compact, become sister chromatids Normal rod shaped chromosomes Protein cohesin help them stick together at centromere 2.) Microtubules depolymerize, mitotic spindle starts formation from raw material Mitotic spindle originates from 2 centrosomes (the MTOC) MTOC starts migrating to opposite poles of cell Because cell needs a lot of tubulin during prophase to make mitotic spindle, going to cause a mass depolymerization of microtubules, and cell use all that raw material of tubulin to reform mitotic spindle Mitotic spindle attach to sister chromatids near centromere region through series of proteins that make up a structure: kinetochore Kinetochore – what attaches microtubules that grow out of centrosome to sister chromatids so it is bound to cohesin and microtubules -Microtubule dramatic dynamic change – because amount of tubulin is needed to be much higher, cell cause most of microtubule to depolymerize at a faster rate before cell enters M phase - Microtubules present during mitosis 1.) Kinetochore microtubule – attaches chromosome to microtubule, bind to cohesin at centromere region of chromosome 2.) Overlapping microtubule – overlap over kinetochore microtubule, require kinesin to separate
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3.) Astral microtubule – anchor centrosome, position where centrosome and spindle is
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Lecture 21 12 - Lecture 21 12/03/07 Mitosis Mitosis -...

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