Stages of Mitosis

1. Interphase

The cell undergoes intense internal activities in preparation for cell division.

These activities include;

• Replication of genetic material (DNA)/chromosomes.
• Synthesis of new cell organelles.eg. golgi apparatus, centrioles, mitochondria, ribosomes.
• Build-up of energy (ATP) to be used during cell division.

2. Prophase

• The duplicated centrioles (in animal cells) separate and move to opposite poles of the cell.
• Spindle fibres begin to form.
• The nuclear membrane begins to break down.
• The nucleolus disappears.
• The chromosomes condense (thicken and shorten and become visible).
• Each chromosome is now seen to consist of a pair of chromatids joined at the centromere.

(c) Metaphase

• The nuclear membrane disappears hence chromosomes are free in the cytoplasm.
• Spindle fibres lengthen. (in animal cells they attach to the centrioles at both poles)
• The chromosomes align themselves at the equator of the spindle and are attached to the spindle fibres by the centromere.

(d) Anaphase

• The sister chromatids separate at the centromere and migrate to the opposite poles. This is caused by the shortening of spindle fibres.
• The spindle apparatus begin to disappear.

(In animal cells, the cell membrane begins to constrict towards the end of anaphase).

(e) Telophase

• The chromatids collect at the two opposite ends of the spindle.
• A nuclear membrane forms around each set of chromatids and are now referred to as chromosomes.
• The cytoplasm divides into two, leading to the formation of two daughter cells.
• The chromosomes become less distinct.

Note:

In animal cells, the division of the cytoplasm is by constriction of cell membrane. However, in plant cells a cell plate forms within the cytoplasm and grows to separate the cell into two.