The structure present inside the nucleus responsible for ribosomal unit formation is

Options

A. Mesosomes
B. Nucleoplasm
C. Nucleolus
D. DNA

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the structure inside the nucleus that is responsible for the formation of ribosomal units.

2. **Identifying the Components of the Nucleus**: The nucleus contains several important components, including genetic material (DNA and RNA), nucleoplasm, and the nucleolus.

3. **Role of the Nucleolus**: The nucleolus is a specific structure within the nucleus that plays a crucial role in the synthesis of ribosomal RNA (rRNA) and the assembly of ribosomal subunits.

4. **Formation of Ribosomal Units**: Inside the nucleolus, ribosomal RNA combines with proteins to form the subunits of ribosomes. This process is essential for the production of ribosomes, which are vital for protein synthesis in the cell.

5. **Evaluating Other Options**:
- **Mesosomes**: Incorrect, as they are invaginations of the plasma membrane found in bacteria, not involved in ribosome formation.
- **Nucleoplasm**: Incorrect, as it is the substance within the nucleus but does not directly form ribosomal units.
- **DNA**: Incorrect, as it serves as genetic material but is not directly involved in the formation of ribosomal units.

6. **Conclusion**: The correct answer to the question is the **nucleolus**, as it is the structure responsible for the formation of ribosomal units.

**Final Answer**: The structure present inside the nucleus responsible for ribosomal unit formation is the **nucleolus**.

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