Definition - What does Nucleus mean?
All eukaryotic cells contain a nucleus, which is a dense organelle situated centrally to the cell and encased in a double membrane, which contains the genetic information of the organism it is found within. The nucleus is often called the brain or control center of a eukaryotic cell. The nucleus contains both DNA and RNA and responsible for growth and reproduction within eukaryotic cell. If a cell is labeled as being prokaryotic, this means it does not have a nucleus and that its genetic information is stored in a piece of DNA attached to the cell membrane and contacting the cytoplasm.
MaximumYield explains Nucleus
In such cases, the genetic information is stored in something called a nucleoid, which does not have a double membrane and is simply a concentration of DNA. It is commonly held that prokaryotic organisms are older and thus have fewer adaptations, and that the forming of a nucleus indicates evolutionary activity toward higher order. This is especially true when one considers the Mitochondria, or the powerhouse of the cell.