Nucleus

The nucleus is a spherical, sometimes elongated structure that contains the genetic material, the DNA, of the cell. It is a very important part of the cell and acts as a "command center". Highly organized chromatin within the nucleus is enclosed by a nuclear membrane. The nuclear membrane contains numerous pores for the transport of large macromolecules and ribosomal subunits to the cytoplasm. The nuclear envelope is actually two parallel unit membranes with an separate perinuclear space. Ribosomes are often attached to the outside membrane and it is sometimes continuous with the rough ER.