Why are histones positively charged?

Options

A. RBC
B. WBC
C. mast cells
D. Bone cells

Answer

### Step-by-Step Solution:

1. **Understanding Histones**: Histones are proteins that play a crucial role in the packaging of DNA in the cell nucleus. They help in forming a structure called nucleosomes, which are essential for DNA organization and regulation.

2. **Composition of Histones**: Histones are rich in basic amino acids. The primary basic amino acids found in histones are lysine and arginine.

3. **Chemical Structure of Basic Amino Acids**:
- **Lysine**: It has an amino group (-NH2) in its side chain, which can accept protons (H+), giving it a positive charge at physiological pH.
- **Arginine**: Similar to lysine, arginine also has a side chain that contains a guanidinium group, which can also accept protons, resulting in a positive charge.

4. **Charge Characteristics**: The presence of these basic amino acids (lysine and arginine) with positively charged side chains contributes to the overall positive charge of histones.

5. **Conclusion**: Therefore, the positive charge of histones is primarily due to the abundance of lysine and arginine, which have positively charged side chains.