Mitosis 1: Prophase

[Animal cell in prophase. Notice that the DNA has been condensed into chromosomes.]

During prophase the chromosomes are identical chromatids connected at the center by a centromere, forming a X-shaped object. The distinguishing feature of prophase is the setup of the mitotic spindle, which is used to maneuver the chromosomes about the cell. The spindle is formed by excess parts from the dismantled cytoskeleton. The spindle is initially setup outside the nucleus.

The cell's centioles are duplicated to form two pairs of centrioles. Each pair becomes the part of the mitotic center which forms the focus for an array of microtubules, called the aster. The two asters lie side by side close the the nuclear envelope. Near the end of prophase the asters pull apart and the spindle is formed.

Continue on to Mitosis 2: Metaphase

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