What is the function of the nucleolus within a cell?

The nucleolus is a prominent structure within the nucleus of eukaryotic cells and plays a specialized role primarily in the production of ribosomal RNA (rRNA). This rRNA is a crucial component of ribosomes, which are the cellular structures where protein synthesis occurs.

The nucleolus assembles rRNA with proteins to form the subunits of ribosomes. Once these subunits are produced, they exit the nucleolus and enter the cytoplasm, where they combine to form functional ribosomes. This process is critical for the overall function of cells because it directly impacts protein synthesis, which is essential for cell growth, function, and repair.

The other functions listed in the choices do not pertain to the nucleolus. For instance, energy production is primarily carried out by mitochondria, while protein synthesis is performed by ribosomes, not the nucleolus itself. Storing genetic material is the role of the nucleus, where DNA resides. Thus, the primary and correct function associated with the nucleolus is the production of ribosomal RNA.