During gel electrophoresis for separation of DNA fragment :

Options

A. smallest fragment will not move to the farthest point
B. smallest fragment will move to the farthest point
C. largest fragment will move to the farthest point
D. lasrgest fragment will move to the farthest point towards anode

Answer

**Step-by-Step Solution:**

1. **Understanding Gel Electrophoresis**: Gel electrophoresis is a technique used to separate DNA fragments based on their size. It involves placing DNA samples in a gel matrix and applying an electric field.

2. **Preparation of DNA Fragments**: Before performing gel electrophoresis, DNA is cut into fragments using restriction endonucleases. These enzymes recognize specific sequences in the DNA and cut it, resulting in various sized fragments.

3. **Charge of DNA**: DNA molecules are negatively charged due to the phosphate backbone. This negative charge is crucial for the movement of DNA in the gel.

4. **Application of Electric Field**: When an electric field is applied, the negatively charged DNA fragments migrate towards the positive electrode (anode). This movement is driven by the electric current.

5. **Use of Agarose Gel**: The gel used in electrophoresis is typically made of agarose. Agarose acts as a medium that provides a sieving effect, allowing for the separation of DNA fragments based on size.

6. **Sieving Effect**: The agarose gel creates a porous structure. Smaller DNA fragments can navigate through the pores more easily and thus move farther in the gel compared to larger fragments, which encounter more resistance.

7. **Separation Based on Size**: As a result of the sieving effect, smaller DNA fragments travel further towards the anode, while larger fragments remain closer to the starting point. This allows for the effective separation of DNA fragments by size.

8. **Conclusion**: Therefore, during gel electrophoresis, the smallest DNA fragments move the farthest towards the positive electrode (anode), confirming that the correct answer is that the smallest fragments will reach the farthest point.

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