In closed mitosis, the nuclear envelope remains intact and chromosomes migrate to opposite poles of a spindle within the nucleus.

(i) Causes unequal distribution of chromosomes.
(ii) Can lead to abnormalities in metabolism and reproduction.

Amitosis is also called direct or incipient cell division. Here there is no spindle formation and chromatin material does not condense.

One of the proteins synthesized only in the G₂ period is known as Maturation Promoting Factor (MPF). It brings about condensation of interphase chromosomes into the mitotic form.

C-Value is the amount in picograms of DNA contained within a haploid nucleus.

Whichever division takes place, it is normally followed by division of the cytoplasm to form separate cells, called as cytokinesis.

In meiosis, the daughter cells contain half the number of chromosomes of the parent cell and is known as haploid state (n).

(i) Control activities of the cell.
(ii) Genetic information copied fro-n cell to cell while the cell divides.

Robert Hooke, Jan Evangelista purkyne (J.E.Purkinje)

1. Genetic stability - Daughter cells are genetically identical to parent cells.
2. Growth - As multicellular organisms grow, the number of cells making up their tissue increases. The new cells must be identical to the existing ones.
3. Repair of tissues - Damaged cells must be replaced by identical new cells by mitosis.