We explain what the nucleus is and some of its characteristics. In addition, its function and how the nucleus cycle is carried out.
What is the nucleus?
In cell biology, it is called a region of the cell nucleus (of the cellular organ that contains the organism's genetic material) where it has place the synthesis of ribosomes (cellular gene translation machines, responsible for the assembly of proteins) and which deals with various cellular tasks.
The nucleus is only within the nucleus, but it is not separated from it by any membrane, since it is considered a supra-macromolecular structure, that is, composed of macromolecules.
His first observations took place accidentally in 1781, a time when cell observation techniques were far from being as powerful as they are today, and he was not recognized. . The formulation of his name and discovery itself occur anan in 1836, when Rudolph Wagner and Gabriel Gustav Valentin will make the first direct observations of the same.
The only one is a structure or region, although it can also be defined as a macromolecular cluster (from biochemistry), which is organized around specific chromosomes that they contain repeated parts of the DNA called Organizing Regions Nucleolar (NORs by its acronym in English). From them, the rest of the chromosomes necessary for the synthesis of ribosomal RNA (rRNA) are organized during the formation of ribosomes.
As for their location, the nucl los usually are within the nucleus but not exactly in the center, but slightly outward. In all eukaryotic cells are found, with the exception of sperm and certain amphibious cells. Its size varies depending on the animal or plant in question (usually between 1 and 3 micrometers), and are usually one to two per cell, although this also It may vary according to species.
See also: Mitochondria.
The main role of this structure is the biosynthesis of ribosomes, to form ribosomal RNA, vital for protein synthesis. In fact, the more intense the protein synthesis activity of a cell, the more nucleoli it will tend to have. Once synthesized, the RNA will mature and be transported from the nucleolus to its destination.
Other functions of the nucleolus involve cell aging, cell stress responses and telomerase activity, an essential ribonucleic enzyme for the elongation of DNA telomeres, that is, vital for genetic duplication and cell division.
This enzyme is abundant in fetal tissue, stem cells and germ cells. Therefore, the nucleolus is involved in the regulation of the cell cycle itself, even though during these stages the nucleolus remains invisible, as if it disappeared. This, of course, during the phases of cell division.
Like chromosomes in the cell nucleus, the nucleolus undergoes an intense series of changes during cell division, a process in which it cannot be seen. During the cell division the nucleolus cycle occurs, which involves three distinct phases:
- Prophetic Disorganization The nucleolus loses size and volume, becoming irregular, to allow the appearance of small masses of its own material, between the prophasic chromosomes that are condensed.
- Metaphase and anaphase transport . The nucleolus loses its individual character and allows its components to join the metaphase chromosomes.
- Telophasic organization . The nucleoli reappear after, in the telophase, the chromosomes are decondensed and lamellar and prenucleolar bodies appear, which will increase in size until one or more nucleoli are formed again.