In agarose gel electrophoresis, DNA molecules are separated on the basis of their

Options

A. charge only
B. size only
C. charge to size ratio
D. all of the above

Answer

To solve the question regarding the separation of DNA molecules in agarose gel electrophoresis, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Agarose Gel Electrophoresis**:
- Agarose gel electrophoresis is a technique used to separate DNA, RNA, or proteins based on their size and charge.

2. **Role of Electric Field**:
- When an electric field is applied, negatively charged DNA molecules move towards the positive electrode. This movement is influenced by their charge.

3. **Separation Mechanism**:
- In the agarose gel matrix, larger DNA fragments encounter more resistance and move slower compared to smaller fragments. Thus, the separation occurs primarily based on size.

4. **Charge Consideration**:
- While DNA is negatively charged and does move in an electric field, the primary factor for separation in agarose gel electrophoresis is the size of the DNA fragments.

5. **Conclusion**:
- Therefore, in agarose gel electrophoresis, DNA molecules are separated primarily on the basis of their size only.

6. **Final Answer**:
- The correct option is **B) size only**.