Cells carry coded information in the form of DNA for regulating
their functions and reproducing themselves. The DNA in some
types of cells floats freely inside the cell. Other cells have a membrane-
bound organelle that contains a cell's DNA. This membranebound
structure is called the nucleus. Most of the functions of a
eukaryotic cell are controlled by the cell's nucleus. The nucleus is
often the most. prominent structure within a eukaryotic cell. It
maintains its shape with the help of a protein skeleton called the
nuclear matrix. The nucleus of a typical animal cell is shown in
Figure 4-6b.