Prophase Metaphase 1. 2. Mitosis START Anaphase Telophase 3. 4.

Prophase In prophase, the chromatin condenses into discrete chromosomes. The nuclear envelope breaks down and spindles form at opposite "poles" of the cell. Many consider prophase to be the first true step of the mitotic process.

Changes That Occur in a Cell During Prophase Chromatin fibers become coiled into chromosomes with each chromosome having two chromatids joined at a centromere. The mitotic spindle, composed of microtubules and proteins, forms in the cytoplasm. In animal cells, the mitotic spindle initially appears as structures called asters which surround each centriole pair.  The two pair of centrioles (formed from the replication of one pair in Interphase) move away from one another toward opposite ends of the cell due to the lengthening of the microtubules that form between them.

In Late Prophase The nuclear envelope breaks up. Polar fibers, which are microtubules that make up the spindle fibers, reach from each cell pole to the cell's equator. Kinetochores attach to a type of microtubule called kinetochore fibers. The kinetochore fibers "interact" with the spindle polar fibers connecting the kinetochores to the polar fibers. The chromosomes begin to migrate toward the cell center.

Prophase Plant Cells Animal Cells

Metaphase In metaphase, the spindle fully develops and the chromosomes align at the metaphase plate (a plane that is equally distant from the two spindle poles). 

Changes That Occur in a Cell During Metaphase The nuclear membrane disappears completely. In animal cells, the two pair of centrioles align at opposite poles of the cell. Polar fibers (microtubules that make up the spindle fibers) continue to extend from the poles to the center of the cell. Chromosomes move randomly until they attach (at their kinetochores) to polar fibers from both sides of their centromeres. Chromosomes align at the metaphase plate at right angles to the spindle poles. Chromosomes are held at the metaphase plate by the equal forces of the polar fibers pushing on the centromeres of the chromosomes.

Metaphase Animal Cells Plant Cells

Anaphase In anaphase, the paired chromosomes (sister chromatids) separate and begin moving to opposite ends (poles) of the cell. Spindle fibers not connected to chromatids lengthen and elongate the cell. At the end of anaphase, each pole contains a complete compilation of chromosomes. 

Changes That Occur in a Cell During Anaphase The paired centromeres in each distinct chromosome begin to move apart. Once the paired sister chromatids separate from one another, each is considered a "full" chromosome. They are referred to as daughter chromosomes. Through the spindle apparatus, the daughter chromosomes move to the poles at opposite ends of the cell. The daughter chromosomes migrate centromere first and the kinetochore fibers become shorter as the chromosomes near a pole. In preparation for telophase, the two cell poles also move further apart during the course of anaphase. At the end of anaphase, each pole contains a complete compilation of chromosomes.

Anaphase Plant Cells Animal Cells

Telophase In telophase, the chromosomes are cordoned off into distinct new nuclei in the emerging daughter cells. 

Changes That Occur in a Cell During Telophase The polar fibers continue to lengthen. Nuclei (plural form of nucleus) begin to form at opposite poles. The nuclear envelopes of these nuclei are formed from remnant pieces of the parent cell's nuclear envelope and from pieces of the endomembrane system. Nucleoli (plural form of nucleolus) also reappear. Chromatin fibers of chromosomes uncoil. After these changes, telophase/mitosis is largely complete and the genetic "contents" of one cell have been divided equally into two.

Telophase Plant Cell Animal Cell

Definitions Spindle Fibers-an aggregate of microtubules that move chromosomes during cell division. Asters-radial microtubule arrays in animal cells which are located around each pair of centrioles. Kinetochores-specialized regions in the centromeres of chromosomes Daughter Cells-chromosome resulting from the separation of sister chromatids.

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