Cell division

Cell division is the process of a biological cell (called a mother cell) dividing into two daughter cells. This leads to growth in multicellular organisms (the growth of tissue) and to procreation (vegetative reproduction) in unicellular organisms.

• Binary fission is the form of cell division used by prokaryotic cells.

• Mitosis is the most common form of eukaryotic cell division. A cell which has reached certain parameters or conditions (size, volume, stored energy, environmental factors, etc.) will replicate its entire nuclear DNA compliment and divide into two (usually equal) daughter cells. Both cells remain diploid or haploid, depending on the mother cell.

• Meiosis is the division of a diploid cell into (four) haploid ones. This cell division is found in multicellular organisms to produce haploid gametes, which can later fuse to form a diploid cell called a zygote.

Multicellular organisms replace worn-out cells through cell division. However, in some animals, cell division eventually halts, and the cell is then referred to as senescent. Senescent cells deteriorate and die, causing the body to age. Cells stop dividing because the telomeres, protective bits of DNA on the end of a chromosome, become shorter with each division and eventually can no longer protect the chromosome. Cancer cells, on the other hand, are "immortal." An enzyme called telomerase allows them to continue dividing indefinitely.