Mitosis occurs in every single cell that makes up the entire body. It occurs in the tissues and organs to help replace cells that have been lost as a result of normal wear and tear on the body.
Mitosis is the replication of a single cell into two identical daughter cells. The original cell becomes obsolete, making the process a simple replication of a single cell. It is used in all areas of the body, but is especially important in the areas that need to have constant regeneration of cells. The skin is an example of an organ that has constant mitosis occurring due to a higher rate of cell loss as a result of environmental factors.
The DNA, or deoxyribonucleic acid, that is composed in the cells is exactly the same throughout the body. The DNA makes up what a person is and must not deviate from the original copies that were made when the person was being developed in utero. When mitosis occurs, the DNA is taken from the cell and is copied exactly how it appeared in the original cell. This process can continue for as long as there is enough energy for mitosis to take place. The DNA will constantly be replicated and will remain the same.