The net electric charge on DNA and histones is

Options

A. both positive
B. both negative
C. Both (a) and (b)
D. zero

Explanation

To determine the net electric charge on DNA and histones, we can break down the components and their charges step by step.

### Step-by-Step Solution:

1. **Understanding DNA Structure**:
- DNA is composed of nitrogenous bases, a pentose sugar, and a phosphate group.
- The phosphate group is negatively charged.

2. **Charge of DNA**:
- Because of the presence of the phosphate groups in the backbone of the DNA, the overall charge of DNA is negative.

3. **Understanding Histones**:
- Histones are proteins that help package DNA into a compact form within the nucleus.
- They are rich in basic amino acids, particularly lysine and arginine.

4. **Charge of Histones**:
- Basic amino acids like lysine and arginine have side chains that carry a positive charge.
- Therefore, histones are positively charged.

5. **Net Electric Charge**:
- Since DNA is negatively charged and histones are positively charged, when they interact, the overall system has both positive and negative charges.
- Thus, the net electric charge on DNA and histones is both positive (from histones) and negative (from DNA).

### Conclusion:
The net electric charge on DNA and histones is both positive and negative.

### Final Answer:
The correct answer is option 3: both positive and negative.

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