Question

Give an account of somatic cell division.

Answer 1

Hint: Remember there are two types of cells in the body namely, somatic and germ cells. Germ cells are haploid and give rise to gametes (sperms and ova), all cells other than gametes are somatic which are diploid and must divide to maintain the body organization.

Complete answer:

(a) Adult diploid somatic cells must undergo regular division to maintain their numbers and structural efficiency. The cell division in somatic cells is different from the cell division in germ cells as the total number of chromosomes in the daughter cells are constant compared to haploid daughter cells that are produced in germ cell division.
(b) The somatic cell division is also known as Mitosis is composed of two main parts first, “karyokinesis”, which is a complex multi-step phenomenon during which the cell nucleus divides, the genetic materials is doubles, nucleus and other cell organelle are dispersed and divided and “cytokinesis” in which the cytoplasm divides to form two cells formed at the end of the process. The detailed step by step observation of karyokinesis is as follows:
(i) Prophase-
The genetic material inside the nucleus begins to condense becomes more visible, while the nucleolus and nuclear envelope slowly disintegrate to release the chromosomes (the condensed genetic material) into the cytoplasm.
The other cellular organelles slowly fragment and recede towards the periphery of the cell.
Spindle fibers begin to emerge out of the centromeres even as they travel towards the poles of the cell.
(ii) Prometaphase-
Chromosomes continue to condense and now possess kinetochores to which the spindle fibers are attached.
Centromeres reach the opposite poles of the cell.
(iii) Metaphase-
Mitotic spindle is developed completely and is attached to the chromosomes (sister chromatids).
Chromosomes travel to the center of the cell and align in a typical “metaphase” plate.
Each chromatid is attached to the spindle fibre from the opposite pole.
(iv) Anaphase-
Proteins keeping the sister chromatids together dissolve and the chromosomes are now split and pulled towards the opposite ends of the cell.
(v) Telophase-
Chromosomes arrive at the opposite poles and begin decondensation.
Nuclear envelope begins re-emerging
Mitotic spindle breaks down.
(vi) Cytokinesis- means the movement of the cell.
Division of cytoplasm following the reconstitution of the nuclear envelope.
In animal cells, the cell division starts from outwards cleaving towards the centre.
However, in the plant cell, the cell division begins from the centre toward the periphery.

Note: All the cells in the human body except the one that produce eggs and sperms are called Somatic cells and they divide regularly and contain two copies of each of their chromosomes. The cell cycle involves two phases namely Interphase and Mitotic phase. The acronym PMAT can be used to remember the four stages of mitotic division, (P-Prophase, M-Metaphase, A-Anaphase and T-Telophase).