If a labelled DNA (with a heavy isotope) replicates in conservative manner in a normal medium then in F1.

Options

A. both daughter DNA molecules will be heavy
B. one DNA molecule will be heavy and one light
C. both DNA molecules will be hybrid
D. all are possible

Answer

To solve the question regarding the replication of labelled DNA with a heavy isotope in a conservative manner, we will follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of DNA Replication**:
- There are three main types of DNA replication: conservative, semi-conservative, and dispersive. In conservative replication, the original DNA molecule remains intact, and a completely new molecule is synthesized.

2. **Identify the Initial Condition**:
- We start with a labelled DNA molecule that has a heavy isotope. This means that the original DNA is heavy (H) and the new DNA synthesized will be light (L) when replicated in a normal medium.

3. **First Replication (F1 Generation)**:
- In conservative replication, after the first round of replication, we will have one molecule that is heavy (H) and one molecule that is light (L). This is because the original heavy DNA does not change and a new light DNA is synthesized.

4. **Analyze the Result of F1 Generation**:
- Therefore, in the F1 generation, we will have:
- 1 heavy DNA molecule (H)
- 1 light DNA molecule (L)

5. **Conclusion**:
- The outcome of this replication process in the F1 generation will yield one heavy and one light DNA molecule. Thus, the correct answer is that in F1 generation, there will be one DNA molecule that is heavy and one that is light.

### Final Answer:
- The F1 generation will consist of one heavy DNA molecule and one light DNA molecule.