MadSci Network: Cell Biology |
It could take months for some cells to divide. It really has a lot to do with what kind of tissue environment the cells are in. For instance, skin cells will divide very rapidly because they are constantly exposed to a bunch of hermful things that can kill a cell like sun light and polution, so damaged cells are replaced from the lower layers of skin cells. On the other hand some cells like brain cells hardely ever divide. They do not divide because the connections "wiring" in the brain needs to be maintained in a very specific way. Now this does not mean that you can just put some brain cells in a hostile environment and they will start to divide more often.Expression of the cells genes tell it how often to divide. A cells genes also tell the cell how many times it can divide before it can not divide any more ( I include this because it seems that you are interested in aging). One gene that plays a role in aging is telomerase. Telomerase is a protein which adds telomere DNA to the end of chromosomes, sort of like caps at the end of shoelaces. Telomeres are on the ends of every chromosome. each telomere has a repeating pattern. In vertebrates the pattern is TTAGGG. Every time the cell divides one TTAGGG is lost. When the telomeres get too short, the cells stop dividing. No one is really sure exactly why some cells divide more than others, but telomerase and telomeres are part of the answer. Skin cells will be able to divide more than brain cells. The human body lives much longer than its individual cells. There is a balance between how often they can divide, and how many times they can divide. OF course this is just one of several theories of aging.
Try the links in the MadSci Library for more information on Cell Biology.