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Mitosis. What is M Phase?. Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two daughter nuclei.
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What is M Phase? • Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two daughter nuclei. • It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two daughter cells containing roughly equal shares of these cellular components.
Four Phases of Mitosis • Prophase 3. Anaphase • Metaphase 4. Telophase (Four phases are followed by Cytokinesis)
Prophase • The first and longest phase of mitosis • The chromosomes become visible. • The centrioles, two tiny structures located in the cytoplasm near the nuclear envelope, separate and take up positions on opposite sides of the nucleus. Centrioles
Prophase • The condensed chromosomes become attached to fibers in the spindle (attach near the centromere of each chromatid). • Near the end of prophase: • The chromosomes coil more tightly • The nucleolus disappears • The nuclear envelope breaks down. Spindle - A fanlike microtubule structure that helps separate the chromosomes.
Metaphase • The second phase of mitosis • The chromosomes line up across the center of the cell, called the metaphase plate. • Microtubules connect the centromere of each chromosome to the two poles of the spindle, called centrioles.
Anaphase • Third phase of mitosis. • The centromeres split, allowing the sister chromatids to separate. • Chromosomes continue to move (pulled by the spindle fibers) until they have separated into two groups near the poles. • Ends when the chromosomes stop moving.
Telophase • Fourth and final phase of mitosis. • The chromosomes begin to disperse into a tangle of dense material. • A nuclear envelope re-forms around each cluster of chromosomes. • The spindle begins to break apart. • A nucleolus becomes visible in each daughter nucleus.
Cytokinesis • Usually occurs at the same time as telophase. • Cytokinesis - The division of the cytoplasm.
Cytokinesis • Animals – cell membrane draws inward & pinches the cell, called the cleavage furrow, into 2 nearly equal parts. • Plants – a cell plate forms midway between the nuclei and gradually develops into the cell wall.
Mitosis Animation Click Here for an Animation Mitosis