Becoming an expert on gel electrophoresis, you are asked to examine a gel for a colleague. Where would you find the smallest segments of DNA ?

Options

A. Near the positive electrode, farthest away from the wells
B. Near the negative electrode, close to the wells.
C. Near the top, near the negative pole.
D. Near the middle, they tend to slow down after the first few minutes.

Answer

To determine where the smallest segments of DNA would be found in a gel during gel electrophoresis, follow these steps:

### Step-by-Step Solution:

1. **Understanding Gel Electrophoresis**:
- Gel electrophoresis is a technique used to separate DNA fragments based on their size. DNA molecules are negatively charged due to their phosphate backbone.

2. **Setup of the Gel**:
- The gel is placed in an electrophoresis chamber with two electrodes: a negative electrode (cathode) and a positive electrode (anode). When an electric current is applied, the DNA fragments migrate towards the positive electrode.

3. **Movement of DNA Fragments**:
- Since DNA is negatively charged, it will move towards the positive electrode. Smaller DNA fragments can navigate through the gel matrix more easily than larger fragments.

4. **Position of DNA Fragments**:
- As the DNA fragments migrate through the gel, smaller fragments will travel further towards the positive electrode compared to larger fragments, which will lag behind.

5. **Conclusion**:
- Therefore, the smallest segments of DNA will be found near the positive electrode, as they have traveled the furthest through the gel.

### Final Answer:
The smallest segments of DNA would be found **near the positive electrode**.

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