What are the two principal roles of the nucleus? What biomolecule is responsible for these roles?

Explanation

### Step-by-Step Solution:

1. **Understanding the Nucleus**: The nucleus is a double membrane-bound organelle found in all eukaryotic cells. It contains the genetic material of the cell.

2. **Principal Roles of the Nucleus**:
- **Role 1: Control and Regulation of Gene Expression**: The nucleus plays a crucial role in controlling gene expression, which involves the processes of replication and transcription. This means that the nucleus regulates which genes are turned on or off, influencing the cell's functions.
- **Role 2: Regulation of Protein Synthesis and Cell Division**: The nucleus also regulates protein synthesis, which is essential for cell function and structure. Additionally, it is involved in the process of cell division, ensuring that genetic material is accurately replicated and distributed to daughter cells.

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