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MITOSIS AND CYTOKINESIS Chapter 9 Section 2
Main Idea Eukaryotic cells replicate by mitosis, the process of nuclear division, and cytokinesis, the process of cytoplasm division.
Mitosis • During mitosis, the cell’s replicated genetic material separates and the cell prepares to split into two cells. • The key activity of mitosis is the accurate separation of the cell’s replicated DNA. • Mitosis: • Increases the number of cells in a multicellular organism as it grows • Replaces damaged cells
The Stages of Mitosis Prophase • Prophase is the first and longest stage of mitosis. • Cell’s chromatin tightens/condenses into chromosomes. • Sister chromatids are structures that contain identical copies of DNA. • The sister chromatids are attached at the centromere. • Nuclear envelope breaks down • Nucleolus breaks down
The Stages of Mitosis Prophase • As prophase continues, spindle fibers, centrioles, and aster fibers form a spindle apparatus. • The spindle apparatus attaches to each of the sister chromatids before cell division.
The Stages of Mitosis Metaphase • The second stage of mitosis is metaphase – the shortest phase. • Sister chromatids are pulled along the spindle apparatus toward the center of the cell. • They line up in the middle of the cell.
The Stages of Mitosis Anaphase • During anaphase, the chromatids pull apart. • The microtubules of the spindle apparatus begin to shorten. • The sister chromatids separate. • The chromosomes move toward the poles of the cell.
The Stages of Mitosis Telophase • Telophase is when the chromosomes arrive at the poles and begin to decondense. • Two new nuclear membranes begin to form and the nucleoli reappear. • The spindle apparatus disassembles.
The Stages of Mitosis Cytokinesis • After the two daughter nuclei have formed, cells undergo cytokinesis. • In animal cells, microfilaments constrict/pinch off to form two cells. • In plant cells, instead of pinching in half, a new structure called the cell plate forms between the two daughter nuclei.
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Thinking Questions What are the events of each stage of mitosis? What is the process of cytokinesis? Copyright © Mc. Graw-Hill Education