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Lecture 19

BIOL 1020 Lecture 19: Lecture 19

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University of Manitoba
Biological Sciences
BIOL 1020
Joy Stacey

Lecture 19 Single stranded chromosomes During S phase chromosome replicates becomes double strandedsister chromatids Attached to one another at the centromere Mitosis= division of eukaryotic cells to make genetically identical cells In G2 chromatin in nucleus(uncondensed DNA 2 stands) In prophase get clear double stranded chromosomes easily visible consist of two sister chromatids attached at centromere Nuclear envelope disappears beginning to migrate along middle plate Chromosomes line up along the middle of the cell Spindle apparatus attaches splits chromosomes to poles of cell single stranded chromosomes Cell splits identical DNA decondenses single stranded G1 Mitotic spindle: Apparatus of microtubules that controls chromosome movement during mitosis During prophase, assembly of spindle microtubules begins in the centrosome, the microtubule organizing center The centrosome replicates, forming two centrosomes that migrate to opposite ends of the cell, as spindle microtubules grow out of them. Only spindles that come half way attach to chromosomes attach on the kinetochore An aster (radial array of short microtubules) extends from each centrosome the spindle includes the centrosomes, the spindle microtubules, and the asters. During prometaphase some spindle microtubules attach to the kinetochores of chromosomes and begin to move the chromosomes At metaphase the chromosomes are all lined up at the metaphase plate, the midway point between the spindles two poles In anaphase, sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell The microtubules shorten by depolymerizing at their kinetochore ends In telophase, genetically identical daughter nuclei form at opposite ends of the cell In animals cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow (contractile ring of microfilaments)
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