Question

Which one of the following is the site for active ribosomal RNA synthesis?

• A. Kinetochore
• B. Centrosome
• C. Chromatin
• D. Nucleolus

Hint:

The Nucleolus is the rRNA factory. No membrane means it can quickly export ribosomal subunits to the cytoplasm!

Answer 1

The Correct Option is D

Step 1: Understanding the Question
The question asks for the specific location within the eukaryotic cell where ribosomal RNA (rRNA) is transcribed and processed. Cells need high amounts of rRNA to build ribosomes, which are the protein-making factories. Step 2: Key Formula or Approach
Recall cell organelle functions. While proteins are made in the cytoplasm, the components of the ribosome (rRNA) are made in a specific "dense" region of the nucleus. Step 3: Detailed Explanation
Centrosome: This is involved in microtubule organization and cell division, not RNA synthesis.
Chromatin: While chromatin contains the DNA that holds rRNA genes, the actual assembly line is localized elsewhere.
Nucleolus: This is a non-membrane-bound structure within the nucleus. It is the site where the large clusters of rRNA genes are located. It is the primary factory for rRNA synthesis and ribosome subunit assembly. Cells that are very active in protein synthesis have larger and more numerous nucleoli.
Kinetochore: These are protein structures on chromosomes where spindle fibers attach during mitosis.
Step 4: Final Answer
The nucleolus is the specialized site for ribosomal RNA synthesis. Thus, (C) is the correct answer.