The primary cells that divide to create new cells in the human body are stem cells. There are different types of stem cells, with different capabilities. There are some that can only create certain types of cells, while others can create almost any type of cell, and some cells that have differentiated can turn back into stem cells. Stem cells not only have the capability to divide to create new cells, but they are flexible enough to turn themselves into different types of cells. The trouble is that this differentiation, with some exceptions, is a one-way process.
Stem cells are multi-potential somatic cells from which other specialized cells come up by differentiation. Stem cells are a group of undifferentiated cells that are able to differentiate into specialized cell types. “In many tissues, stem cells serve as a sort of internal repair system, dividing essentially without limit to replenish other cells as long as the person or animal is still alive” (Teresa, 2006). Stem cells are categorized by their potential to differentiate into other types of cells. Embryonic stem cells are the most potent since they must become every type of cell in the body. Stem cells exhibit two characteristics not found in more differentiated cells. They can also give rise to a wide range of mature cells types. Stem cells also help to construct the body, from a small number of cells, in the early development of the body.
Stem cells are capable of dividing and renewing themselves for long periods. “Stem cells have the ability to divide infinitely and develop into a huge variety of specialized cells required for the creation of an organism” (Hoyle, 2010). Unlike muscle cells, blood cells, or nerve cells, stem cells may replicate and make copies of themselves many times. Stem cells remain undifferentiated and give rise to specialized cells and can help repair tissues and organs. Stem cells help replace cells that die off over time and they can also grow tissues and organs. When a stem cell divides, it can make up to two hundred- twenty different cells.
Stem cells come in good use because not all cells divide. Stem cells are needed to make up for this. Some cells do not divide because of enzymes, which control the genes of the cell by turning them on or off. “Genes are turned off until a metabolite inactivates the repressor allowing transcription to take place” (Constance, 2010). This would take place if there was glucose available to the bacteria so that it would not have to use lactose as a food supply. The genes have always been there, they are only required if the environment considers it beneficial. In bacteria and all organisms, gene expression can be turned on or turned off by signals from outside a cell coming from some other part of the body or even from the environment outside the organism. External signals interact with transcription factors to either activate or inactivate the transcription of a gene by RNA polymerase.
There are two...