what does the nucleolus do
The nucleolus is the nuclear subdomain that assembles ribosomal subunits in eukaryotic cells. The nucleolar organiser regions of chromosomes, which contain the genes for preâribosomal ribonucleic acid (rRNA), serve as the foundation for nucleolar structure.ey Concepts. 1  The nucleolus, whose primary function is to assemble ribosomes, is the largest structure in the cell nucleus. 2  The nucleolus organiser regions of chromosomes, which harbour the genes for preârRNA, are the foundation for the nucleolus.