Which of the following is true for nucleolus ?

Options

A. It is site for active ribosomol RNA synthesis.
B. It takes part in spindle formation
C. It is a membrance-bound structure.
D. Larger nucleoli are present in dividing cells

Answer

To determine which statement is true about the nucleolus, we can analyze the provided options step by step:

### Step 1: Understand the Function of the Nucleolus
The nucleolus is a prominent sub-structure within the nucleus of eukaryotic cells. Its primary function is the synthesis of ribosomal RNA (rRNA) and the assembly of ribosome subunits.

**Hint:** Remember that the nucleolus is involved in ribosome production.

### Step 2: Evaluate the Options
Now, let's evaluate each option given in the question:

1. **It is a site for active ribosomal RNA synthesis.**
- This statement is true. The nucleolus is indeed the site where rRNA is synthesized and where ribosomal subunits are assembled.

2. **It takes part in spindle formation.**
- This statement is false. The nucleolus does not play a role in spindle formation; that function is primarily associated with the centrosome and microtubules during cell division.

3. **It is a membrane-bound structure.**
- This statement is false. The nucleolus is not membrane-bound; it is a dense region within the nucleus that forms around specific chromosomal regions.

4. **Large nuclei are present in dividing cells.**
- This statement is somewhat misleading. While some dividing cells may have larger nuclei due to increased activity, it is not a definitive characteristic of all dividing cells.

### Step 3: Identify the Correct Statement
Based on the evaluations, the correct statement about the nucleolus is:
- **It is a site for active ribosomal RNA synthesis.**

### Conclusion
Thus, the answer to the question is that the nucleolus is primarily known for being the site of active ribosomal RNA synthesis.

**Final Answer:** Option A: It is a site for active ribosomal RNA synthesis.