why some cells divides in shorter period while some require more time?
Answers
Explanation:
The length of the cell cycle is important because it determines how quickly an organism can multiply. For single-celled organisms, this rate determines how quickly the organism can reproduce new, independent organisms. For higher-order species the length of the cell cycle determines how long it takes to replace damaged cells. The duration of the cell cycle varies from organism to organism and from cell to cell. Certain fly embryos sport cell cycles that last only 8 minutes per cycle! Some mammals take much longer than that--up to a year in certain liver cells. Generally, however, for fast-dividing mammalian cells, the length of the cycle is approximately 24 hours.
Most of the differences in cell cycle duration between species and cells are found in the duration of specific cell cycle phases. DNA replication, for example, generally proceeds faster the simpler the organisms. One reason for this trend is simply that prokaryotes have smaller genomes and not as much DNA to be replicated. Across species and organismal complexity, embryonic cells have an increased need for rapidity in the cell cycle because they need to multiply for the development of the embryo. Early embryonic cell cycles often omit G1 and G2 and quickly proceed through successive rounds of S phase and mitosis. For these cells, the main concern is not the regulation of the cell cycle (which occurs largely in G1 and G2), but rather in the speed of cell proliferation.