Final answer:
Eukaryotic ribosomal RNA is transcribed in the nucleolus of the nucleus in eukaryotic cells and is essential for the assembly of ribosomes, which are critical for protein synthesis.
Step-by-step explanation:
Eukaryotic ribosomal RNA (rRNA) is transcribed in the nucleolus, which is a small dense spherical structure in the nucleus of eukaryotic cells. The nucleolus is responsible for the synthesis of ribosomal RNA and initiating the assembly of ribosomes, which are essential for protein synthesis. Eukaryotic ribosomes are composed of small and large subunits, which are made up of ribosomal RNA and ribosomal proteins. These ribosomes can either be bound to the membrane of the rough endoplasmic reticulum or be free in the cytoplasm. Additionally, within the mitochondria and chloroplasts of eukaryotic cells, ribosomes are similar to those found in prokaryotes, called 70S ribosomes.