What is the criterion for DNA fragments movement on agarose gel during get electrophoresis

Options

A. The larger the fragment size, the farther it moves
B. The smaller the fragment size, the farther it moves
C. Positively charged fragments move to farther end
D. Negatively charged fragments do not move

Answer

### Step-by-Step Solution:

1. **Understanding Electrophoresis**: Electrophoresis is a technique used to separate DNA fragments based on their size. It involves applying an electric current to a gel medium (agarose gel) that contains the DNA samples.

2. **Charge of DNA**: DNA molecules are negatively charged due to their phosphate backbone. When an electric current is applied, the negatively charged DNA will migrate towards the positive electrode.

3. **Movement of DNA Fragments**: The movement of DNA fragments through the gel is influenced by their size. Smaller DNA fragments can navigate through the pores of the gel more easily than larger fragments.

4. **Sieving Effect**: The gel acts as a sieve, allowing smaller fragments to move faster and farther than larger fragments. This phenomenon is known as the sieving effect.

5. **Evaluating Options**:
- **Option 1**: "The larger the fragment size, the farther it moves." - This is incorrect because larger fragments move slower and do not travel as far.
- **Option 2**: "The smaller the fragment size, the farther it moves." - This is correct as smaller fragments can move faster through the gel.
- **Option 3**: "Positively charged fragments move to farther ends and negatively charged fragments do not move." - This is incorrect because DNA is negatively charged and moves towards the positive electrode.

6. **Conclusion**: The correct criterion for the movement of DNA fragments during gel electrophoresis is that smaller fragments move farther than larger fragments.

### Final Answer:
The correct criterion for DNA fragment movement on agarose gel during gel electrophoresis is: **The smaller the fragment size, the farther it moves.**

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