Student Projects/Cell division

CELL DIVISION

Cell division, cell reproduction or cell multiplication is the process of formation of new or daughter cells from the pre-existing or parent cells.

TYPES

1. Amitosis or Direct cell division.

2. Mitosis or Indirect cell division.

3. Meiosis or Reductional cell division

Amitosis (Direct Cell Division):

(GK. a = no, mitosis = thread, osis = state)

Amitosis is a mode of division in which nucleus elongates, constricts in the middle and divides directly into two daughter nuclei. This is followed by centripetal constriction of cytoplasm to form two daughter cells.

Occurance :

mega-nucleus of paramecium, nuclei of internodal cells of Cham, endosperm cells of seeds, cartilage cells and diseased cells

Mitosis (Indirect Cell Division)/ (Equational Cell Division):

(GK. Mitos = thread, osis = state)

Mitosis is a type of cell division in which chromosomes are equally distributed resulting in two genetically identical daughter cells.

Occurrence:

The cells undergoing mitosis are called mitocytes. In plants, the mitocytes are mostly meristematic cells. In animals, the mitocytes are stem cells, germinal epithelium & embryonic cells. It also occurs during regeneration. Root tip is the best material to study mitosis.

Meiosis (Reductional Cell Division):

(Gr. meioum = to reduce, osis = state)

Meiosis is a double division in which a diploid cell divides twice to form four haploid daughter cells.

Occurrence:

The cells undergoing meiosis are called meiocytes. In plants, the meiocytes are microsporocytes (Pollen mother cell) of anthers and megasporocytes (megaspore mother cell) of ovules. In animals, the meiocytes are primary spermatocytes in testes and primary oocytes in ovaries.