About Lesson
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.
