CHAPTER 5 CELL DIVISION -Introduction

Cell division is the process by which a cell replicates to form two essentially identical daughter cells; the process includes the four stage nuclear division, mitosis, and cytoplasmic division = cytokinesis; upon completion of the process, each daughter cell contains the same genetic material, exact copies of the DNA, as the original cell and roughly half of its cytoplasm.

Mitosis is the process of nuclear division of either a diploid (2N) or haploid (N) eukaryotic cell whereby two daughter nuclei are produced that are genetically identical to the parent nucleus. Cell division usually follows nuclear division.

Mitosis usually results in the production of two progeny cells that are genetically identical to the parent cell.

Mitosis is a continuous process and divided into 4 main phases based on the appearance and behavior of the chromosomes.

1.      Prophase, P

2.      Metaphase, M

3.      Anaphase, A

4.      Telophase, T

The significance of mitosis

1.      Growth. The number of cells within an organism increases by mitosis and this is the basis of growth in multicellular organisms.

2.      Cell Replacement. Cells are constantly sloughed off, dying and being replaced by new ones in the skin and digestive tract. When damaged tissues are repaired, the new cells must be exact copies of the cells being replaced so as to retain normal function of cells.

3.      Regeneration. Some animals can regenerate parts of the body, and production of new cells are achieved by mitosis.

4.      Vegetative Reproduction. Some plants produce offspring which are genetically similar to themselves. These offspring are called clones.

Red blood cells have short live spans of about 4 months and need to be replaced constantly by mitosis.