Which term describes a non-membrane-bound structure in the nucleus that builds ribosomes?

Which term describes a non-membrane-bound structure in the nucleus that builds ribosomes?

• A. Nucleolus
• B. Nucleus
• C. Vesicle
• D. Ribosome

Answer: (A)

The nucleus contains a dense, membrane-free region where ribosome production happens. This structure, formed around ribosomal DNA gene clusters, transcribes and processes ribosomal RNA and begins assembling ribosomal subunits by combining rRNA with ribosomal proteins imported from the cytoplasm. These subunits are then sent to the cytoplasm to finish assembling into mature ribosomes. The other options don’t fit because a vesicle is membrane-bound, a ribosome is the finished particle, and the nucleus is the whole membrane-bound organelle, not a specialized non-membrane compartment. So the term described is nucleolus.

The nucleus contains a dense, membrane-free region where ribosome production happens. This structure, formed around ribosomal DNA gene clusters, transcribes and processes ribosomal RNA and begins assembling ribosomal subunits by combining rRNA with ribosomal proteins imported from the cytoplasm. These subunits are then sent to the cytoplasm to finish assembling into mature ribosomes. The other options don’t fit because a vesicle is membrane-bound, a ribosome is the finished particle, and the nucleus is the whole membrane-bound organelle, not a specialized non-membrane compartment. So the term described is nucleolus.