The Cell Cycle & Mitosis Tutorial

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• cell is engaged in metabolic activity and performing its prepare for mitosis (the next four phases that lead up to and include nuclear division).

• Chromosomes are not clearly discerned in the nucleus, although a dark spot called the nucleolus may be visible.

• may contain a pair of centrioles (or microtubule organizing centers in plants) both of which are organizational sites for microtubules.

• Chromatin in the nucleus begins to condense and becomes visible in the light microscope as chromosomes.

• nucleolus disappears

• entrioles begin moving to opposite ends of the cell and fibers extend from the centromeres.

• nuclear membrane dissolves, marking the beginning of prometaphase.

• Proteins attach to the centromeres creating the kinetochores. Microtubules attach at the kinetochores and the chromosomes begin moving.

• Spindle fibers align the chromosomes along the middle of the cell nucleus.

• line is referred to as the metaphase plate.

• organization helps to ensure that in the next phase, when the chromosomes are separated, each new nucleus will receive one copy of each chromosome.

• paired chromosomes separate at the kinetochores and move to opposite sides of the cell.

• results from a combination of kinetochore movement along the spindle microtubules and through the physical interaction of polar microtubules.

• Chromatids arrive at opposite poles of cell, and new membranes form around the daughter nuclei.

• chromosomes disperse and are no longer visible under the light microscope

• pindle fibers disperse, and cytokinesis or the partitioning of the cell may also begin during this stage.

• animal cell

• cytokinesis results when a fiber ring composed of a protein called actin around the center of the cell contracts pinching the cell into two daughter cells, each with one nucleus.

• lant cells

• rigid wall requires that a cell plate be synthesized between the two daughter cells.