What part of the nucleus is responsible for making ribosomes?

The portion of the nucleus responsible for making ribosomes is the nucleolus. This structure is a dense region within the nucleus where ribosomal RNA (rRNA) is synthesized and combined with proteins to form the subunits of ribosomes. These ribosomal subunits are then transported out of the nucleus into the cytoplasm, where they assemble into functional ribosomes that play a crucial role in protein synthesis.

The nucleolus is distinct from the rest of the nucleus, which primarily functions in housing genetic material and coordinating cellular activities, including cell division and gene expression. Other options such as the vacuole, which is involved in storage and maintaining cell turgor pressure, and the rough endoplasmic reticulum (ER), which participates in protein synthesis and processing, do not have a direct role in the assembly of ribosomes. Thus, the nucleolus is specifically designed for this vital function in the overall cellular machinery.