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

Question

Accepted Answer

C. 1. Recall the structure and function of the **nucleolus**.
The nucleolus is a dense, non-membrane-bound spherical structure present inside the nucleus, and it is closely associated with specific regions of chromatin called **nucleolar organizer regions**.

2. Connect this structure to its main role.
Since these regions carry the genes for ribosomal RNA (rRNA), the nucleolus is the site of **active rRNA synthesis** and ribosome subunit assembly.

3. Eliminate the other options.
**Centrosome** organizes microtubules and spindle fibers, **chromatin** is the DNA-protein complex forming chromosomes, and **kinetochore** is the protein structure where spindle fibers attach during cell division — none synthesize rRNA.

Hence, the answer is **C. Nucleolus**.