Cell Division

1        Not all cells are dividing.

2        A cell that is not dividing is said to be in interphase. Here, the cell is growing and active.

3        After a certain “growth span” the cell prepares itself to divide.

4        The duplication of the nucleus is the first and most important, part of cell division called mitosis.

5        After mitosis is complete the rest of the cell contents are more or less evenly divided between the two new cells (daughter cells) called cytokinesis.

Interphase à Mitosis (PMAT) à Cytokinesis.

Interphase

6        Chromatin in the nucleus is a tangled mass of fine fibers.

7        Towards the end of Late Interphase the DNA in the chromatin replicates. The number of chromatin threads double.

Mitosis

Prophase

8        The doubled chromatin strands shorten and thicken into chromosomes.

9        Each chromosome consists of a pair of chromatids held together by a centromere.

10    In the animal cell the two centrioles split apart and move to opposite ends of the cell (the poles).

11    When the centrioles are in place, fibres called spindles are projected outwards from each centriole.

12    The fibers projected towards the middle of the cell become attached to the centromere of each chromatid pair (spindle fibers).

Metaphase

13    The chromosomes line up along the area in the middle of the cell called the equator.

14    The centromere holding the chromatids together split apart, separating the chromatids.

15    The single chromatids are “chromosomes”.