A: Ethidium bromide helps in visualizing DNA in UV light only.
R: This intercalating agent absorbs light in range 260-330 nm.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion
C. If Assertion is true statement but Reason is false
D. If both Assertion and Reason are false statements

Answer

To solve the question, we need to analyze the assertion and the reason provided:

### Step 1: Analyze the Assertion
The assertion states: "Ethidium bromide helps in visualizing DNA in UV light only."
- Ethidium bromide is a fluorescent dye that intercalates between the bases of DNA.
- It emits an orange fluorescence when exposed to UV light, which allows for the visualization of DNA bands in gel electrophoresis.

**Conclusion for Step 1**: The assertion is true.

### Step 2: Analyze the Reason
The reason states: "This intercalating agent absorbs light in the range 260-330 nm."
- Ethidium bromide indeed absorbs UV light in this range (260-330 nm), which is why it can fluoresce and allow for visualization of DNA.
- This property of ethidium bromide as an intercalating agent is crucial for its function in DNA visualization.

**Conclusion for Step 2**: The reason is also true and provides a correct explanation for the assertion.

### Step 3: Determine the Relationship
Since both the assertion and the reason are true, and the reason correctly explains why the assertion is true, we conclude that the correct option is:

**Answer**: Option A - Both assertion and reason are true, and reason is the correct explanation of assertion.