Cellular Nucleus

The DNA-containing nucleus has been described as a balloon filled with thick solution with a fibrous mesh which holds the DNA in place and which moves molecules about.

The major components of the nucleus include the chromosomes, the nucleolus, the nucleoplasm, and the nuclear cortex. Chromosomes are made of DNA; the nucleolus manufactures ribosomal components; and the nucleoplasm is the fluid and filaments inside the nucleus. The nuclear cortex is a dense area on the inner face of the nucleus, which tethers the chromosomes in place when the cell is not undergoing division.

Not all cells have a nucleus. Bacterial cells lack a nucleus and so do the red blood cells of mammals. Red blood cells (or corpuses) need to be flexible enough to get into tiny capillaries to deliver oxygen and nutrients to the cells. Some cells have more than one nucleus (multinucleated), for example, nutrient-providing cells in the garden pea plant and lilies both have some multi-nucleated, nutrient-providing cells. The long, tube-like skeletal muscle cells in vertebrates are also multinucleated.