The nucleus contains all the genetic material in a cell. This genetic information is called deoxyribonucleic acid (DNA). DNA contains all the instructions for making proteins, which control all of the body’s activities. Therefore, the nucleus is like the manager’s office of the cell.
DNA is an extremely precious and tightly regulated molecule. Therefore, it does not just exist naked in the nucleus! Instead, DNA is tightly wound around structural proteins called histones to form chromatin. When the cell is ready to divide to pass the genetic information on to new cells (the daughter cells), the chromatin forms highly condensed structures called chromosomes.
The nucleus regulates which genes are turned ‘on’ in the cell, and at what time. This controls the cell’s activity. The genes that are active at a given time will be different depending on the type of cell and the function it performs.
The nucleus is surrounded by a nuclear envelope (also called the nuclear membrane), which separates it from the rest of the cell. The nuclear envelope also contains pores that permit the entry and exit of some molecules.
As well as all the genetic material, there is also a sub-section of the nucleus called the nucleolus, which looks like a nucleus within the nucleus. The nucleolus is the site of ribosome synthesis. The nucleus is surrounded by a nuclear envelope (also called nuclear membrane), which separates it from the rest of the cell.
The nucleus also regulates the growth and division of the cell. When the cell is preparing to divide during mitosis, the chromosomes in the nucleus duplicate and separate, and two daughter cells form. Organelles called centrosomes help to organize the DNA during cell division.
The nucleus contains DNA in the form of chromatin. Chromatin can be further compacted to form chromosomes. The nucleus is surrounded by a double envelope that contains pores to allow certain materials to pass in and out. The nucleus also contains a region called the nucleolus.