Mitogens

Mitogens

The factors which promote cell cycle proliferation is called mitogens. Plant mitogens include gibberellin, ethylene, Indole acetic acid, kinetin. These increase mitotic rate.

Mitotic Poisons (Mitotic Inhibitors)

Certain chemical components act as inhibitors of the mitotic cell division and they are called mitotic poisons.

Endomitosis

The replication of chromosomes in the absence of nuclear division and cytoplasmic division resulting in numerous copies within each cell is called endomitosis. Chromonema do not separate to form chromosomes, but remain closely associated with each other. Nuclear membrane does not rupture. So no spindle formation. It occurs notably in the salivary glands of Drosophila and other flies. Cells in these tissues contain giant chromosomes (polyteny), each consisting of over thousands of intimately associated, or synapsed, chromatids. Example: Polytene chromosome.

Anastral

This is present only in plant cells. No asters or centrioles are formed only spindle fibres are formed during cell division.

Amphiastral

Aster and centrioles are formed at each pole of the spindle during cell division. This is found in animal cells.