Nucleolus takes part in synthesis of

Options

A. rRNA
B. tRNA
C. mRNA
D. DNA

Answer

### Step-by-Step Solution:

1. **Identify the Role of the Nucleolus**: The nucleolus is a dense, spherical structure located within the nucleus of a cell. Its primary function is to synthesize certain types of RNA.

2. **Types of RNA**: There are several types of RNA in the cell, including:
- Ribosomal RNA (rRNA)
- Transfer RNA (tRNA)
- Messenger RNA (mRNA)
- DNA (deoxyribonucleic acid)

3. **Synthesis Locations**:
- **Ribosomal RNA (rRNA)**: The synthesis of rRNA occurs specifically in the nucleolus.
- **Transfer RNA (tRNA)** and **Messenger RNA (mRNA)**: The synthesis of these types of RNA takes place in the nucleus, but not in the nucleolus.
- **DNA**: DNA synthesis or replication also occurs in the nucleus, but again, not in the nucleolus.

4. **Function of Ribosomal RNA**: Ribosomal RNA is a key component of ribosomes, which are the cellular structures responsible for protein synthesis. Ribosomes are made up of ribosomal proteins and ribosomal RNA.

5. **Conclusion**: Based on the information gathered, we can conclude that the nucleolus is primarily involved in the synthesis of ribosomal RNA.

6. **Final Answer**: Therefore, the correct answer to the question "Nucleolus takes part in synthesis of" is **ribosomal RNA**.