In double stranded helical structure of DNA each step of ascent, the strand turns by

Options

A. `26^(@)`
B. `36^(@)`
C. `34^(@)`
D. `48^(@)`

Answer

To solve the question regarding the turn of the DNA strand in its double-stranded helical structure, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of DNA**:
- DNA is a double-stranded helical structure, which means it consists of two strands that twist around each other.

2. **Identify the Components of the Helix**:
- Each "step" of the helix corresponds to a pair of nitrogenous bases (adenine-thymine or guanine-cytosine) that are bonded together.

3. **Determine the Angle of Turn**:
- As the DNA helix ascends, it turns at a specific angle with each step. This angle is crucial for understanding the helical nature of DNA.

4. **Review the Options Provided**:
- The options given are:
- A) 26 degrees
- B) 36 degrees
- C) 34 degrees
- D) 48 degrees

5. **Recall the Known Information**:
- From scientific studies and models, it is known that the DNA helix turns approximately 36 degrees for each base pair.

6. **Select the Correct Answer**:
- Based on the information recalled, the correct answer is **B) 36 degrees**.

### Final Answer:
The strand turns by **36 degrees** for each step of ascent in the double-stranded helical structure of DNA.

---