Which of the following is correct about the thermal ends of a linear DNA chain?

Options

A. 5' phosphate end 3' phosphate end
B. 5' phosphate end and 3' OH end
C. 5' OH end 3' phosphate end
D. 5' OH end and 5' OH end

Answer

To solve the question regarding the thermal ends of a linear DNA chain, let's break down the information step by step.

### Step-by-Step Solution:

1. **Understanding DNA Structure**:
- DNA is structured as a double helix, consisting of two strands that run in opposite directions. Each strand has a directionality defined by its ends: the 5' (five prime) end and the 3' (three prime) end.

2. **Identifying the Ends**:
- The 5' end of a DNA strand has a phosphate group attached to the fifth carbon of the sugar molecule (deoxyribose).
- The 3' end has a hydroxyl group (-OH) attached to the third carbon of the sugar.

3. **Analyzing the Options**:
- The options provided in the question need to be evaluated based on the structure of DNA:
- **Option 1**: 5' phosphate and 3' phosphate (Incorrect)
- **Option 2**: 5' phosphate and 3' hydroxyl (Correct)
- **Option 3**: 5' hydroxyl and 3' phosphate (Incorrect)
- **Option 4**: 5' hydroxyl and 5' hydroxyl (Incorrect)

4. **Conclusion**:
- The correct description of the thermal ends of a linear DNA chain is that the 5' end has a phosphate group and the 3' end has a hydroxyl group. Therefore, the correct answer is **Option 2: 5' phosphate and 3' hydroxyl**.