Determine the representation of the Nucleus
In all eukaryotic cells, the nucleus represents the most prominent and conspicuous organelle of the cell, and is generally seen as a large dense body by special staining procedures, since in a living cell it generally appears structure less. The nucleus is surrounded by a double membrane with pores, which allow selective passage of materials into and out of the nucleus. The nucleus being the "control centre" of the cell, it contains chromatin, composed of DNA, which is associated with a set of five basic proteins called the histones. Histones are small proteins with molecular weights ranging from 11,000 to 21,000 and these contain a very high content of the basic amino acids, namely lysine and arginine (about 25%). Eukaryotic cells contain considerably more DNA than prokaryotes. Thus, while the E.coli cell has an aggregate DNA content of 4 x lo6 base pairs, that of yeast has 1.35 x 107 base pairs, and the human cell has 2.9 x 109 base pairs. Much of the DNA in a eukaryotic cell does not code for proteins, and is regarded as "junk" DNA, the function of which is not clearly understood as yet.