Differentiation Link

        This process of cell differentiation is difficult for students.  (That may be why
        you are now at this page.) 

        All cells start out with identical DNA.  In humans that same DNA is used to
        make a whole bunch of different types of cells.  We have red blood cells, white
        blood cells, skin cells, kidney cells, lung cells etc.

        Each of these cells that is nucleated (red blood cells lost their nuclei early in
        their development) has identical DNA.  But the white blood cells, due to
        environmental influences only "read" the DNA chapters on how to become
        white blood cells.   The skin cells only "read" the DNA chapters on how to
        become skin cells and ignore the unrelated DNA.  

        In this manner, a great variety of human cells, despite identical DNA,
        differentiate into different cells both in their appearance and in their functions.