noun, plural mitoses
The somatic cells of eukaryotes go through a sequence of biological events called cell cycle. The cell cycle is comprised of these fundamental events: (1) resting phase (Gap 0), (2) interphase (Gap 1, S phase, Gap 2), and (3) cell division (i.e. mitotic phase and cytokinesis). In essence, the cell may enter either the resting phase or the interphase following cell division. If it enters the interphase, the cell would prepare itself for cell division by replicating its DNA during the S phase. Prior to entering the mitotic phase, the cell has a control mechanism called G2-M DNA damage checkpoint that ensures the cell is ready for mitosis. Mitosis is comprised of four major phases which culminates in the formation of two identical (daughter) cells:
- 1st phase: Prophase: formation of paired chromosomes, disappearance of nuclear membrane, appearance of the achromatic spindle, formation of polar bodies
- 2nd phase: Metaphase: arrangement of chromosomes in the equatorial plane. Chromosomes separate into exactly similar halves.
- 3rd phase: Anaphase: the two groups of daughter chromosomes separate and move along the fibres of the central spindle, each toward one of the asters, forming the diaster.
- 4th phase: Telophase: two daughter nuclei are formed, the cytoplasm divides, forming two complete daughter cells.
Originally, the term mitosis refers only to nuclear division unaccompanied by cytokinesis (which is the division of the cytoplasm), as in the case of some cells like certain fungi and in fertilized egg of many insects. As used now, mitosis used interchangeably with cell division.
Word origin: Greek mitos (warp thread) + –osis
- mitotic (adjective)
- mitotically (adverb)