If an isolated strain of DNA is kept at 82- `90^(@)` C , then

Options

A. It change into RNA
B. It divides into one million pieces
C. No effect
D. It uncoils into helixes

Explanation

To solve the question regarding the effect of keeping an isolated strain of DNA at 82 to 90 degrees Celsius, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding DNA Structure**:
- DNA is composed of two strands that form a double helix. The strands are held together by hydrogen bonds between complementary bases.

2. **Effect of Temperature on DNA**:
- Increasing the temperature can disrupt the hydrogen bonds that hold the two strands of DNA together. This process is known as denaturation.

3. **Temperature Threshold**:
- The temperature range mentioned (82 to 90 degrees Celsius) is sufficient to break the hydrogen bonds between the DNA strands, leading to the separation of the strands.

4. **Analyzing the Options**:
- **Option A**: Changes into RNA - This is incorrect as DNA does not convert to RNA at high temperatures; that process is called transcription, which occurs under different conditions.
- **Option B**: Divides into 1 million pieces - This is also incorrect; while the DNA may denature, it does not break into numerous pieces.
- **Option C**: Has no effect - This is incorrect because the high temperature will have a significant effect on the DNA structure.
- **Option D**: Uncoils into helix - This option is misleading. While the DNA does uncoil, it does not form a helix; instead, it separates into single strands.

5. **Conclusion**:
- The correct interpretation of the effect of high temperature on DNA is that it uncoils and separates into single strands, but it does not form a new helix. Therefore, the best answer among the options provided is option D, considering the context of the question.

### Final Answer:
**Option D: It uncoils into helix.** (Note: This is a bit misleading as it implies a new helix formation, but it is the closest option to the correct concept of uncoiling.)