The separated DNA fragment can be visualized only after staining the DNA with

Options

A. ethidium sulphide
B. ethidium bromide
C. ethidium sulphide
D. ethidium bromite

Answer

To solve the question regarding the visualization of separated DNA fragments, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which staining agent is used to visualize separated DNA fragments after electrophoresis.

2. **Knowledge of DNA Separation**: DNA fragments are separated based on their size using agarose gel electrophoresis. The DNA is negatively charged and moves towards the positive electrode.

3. **Staining Agents**: There are various staining agents that can be used to visualize DNA. Some common ones include:
- Ethidium Bromide
- Ethidium Sulfate
- Ethidium Sulfide

4. **Identifying the Correct Staining Agent**: Among the options provided:
- Ethidium Bromide is a well-known intercalating agent that binds to DNA and fluoresces under UV light, allowing for visualization of the DNA bands.
- Ethidium Sulfate and Ethidium Sulfide are not commonly used for this purpose.

5. **Conclusion**: Based on the knowledge of DNA visualization techniques, the correct answer is **B. Ethidium Bromide**. This compound is specifically used to stain DNA fragments, making them visible as orange bands when exposed to UV light.

### Final Answer:
The separated DNA fragment can be visualized only after staining the DNA with **B. Ethidium Bromide**.