Myosin is plentiful in muscle cells, but is not found at all in lens cells. Lens cells contain large amounts of crystallins, which are not found in muscle cells. Why do some proteins appear in one type of cell but not in another?

There are few cells in the body that do not undergo mitosis: most somatic cells divide regularly, some more than others. take for example the cells that line the digestive tract. these cells must be frequently replaced because they are constantly eroded by the movement of food through the tract. what mechanism(s) is/are in place to ensure that these cells are exact copies of the mother cell