Final answer:
The nucleus is the command center of the cell and contains the genetic material. It is encased within a nuclear envelope and contains nucleoli for ribosome synthesis. DNA is found as chromatin within the nucleus, which condenses into visible chromosomes during cell division.
Step-by-step explanation:
The nucleus is the command center of the cell, containing the genetic instructions for all of the materials a cell will make (and thus all of its functions it can perform). The nucleus is encased within a membrane of two interconnected lipid bilayers, side-by-side. This nuclear envelope is studded with protein-lined pores that allow materials to be trafficked into and out of the nucleus.
The nucleus contains one or more nucleoli, which serve as sites for ribosome synthesis. The nucleus houses the genetic material of the cell: DNA. DNA is normally found as a loosely contained structure called chromatin within the nucleus, where it is wound up and associated with a variety of histone proteins. When a cell is about to divide, the chromatin condenses into visible chromosomes which can be seen under a microscope.