Length of one coil of B-DNA helix is

Options

A. 0.34 nm
B. 3.4 nm
C. `3.4Å`
D. `0.34Å`

Answer

To determine the length of one coil of the B-DNA helix, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding B-DNA Structure**: B-DNA is a double helical structure that consists of two strands of nucleotides. Each complete turn of the helix is referred to as a coil.

2. **Pitch of B-DNA**: The pitch of the B-DNA helix is defined as the distance between one complete turn of the helix. This is the length of one coil.

3. **Base Pairs in One Coil**: It is known that one complete coil of B-DNA contains approximately 10 nucleotide base pairs.

4. **Length of One Coil**: The total length of one coil (or pitch) of B-DNA is approximately 3.4 nanometers. This means that the distance covered by 10 base pairs in one complete turn of the helix is 3.4 nanometers.

5. **Distance Between Base Pairs**: To find the distance between one nucleotide base pair, we can divide the total length of one coil by the number of base pairs:
\[ \text{Distance between one base pair} = \frac{3.4 \text{ nm}}{10} = 0.34 \text{ nm} \]

6. **Final Answer**: Therefore, the length of one coil of B-DNA helix is 3.4 nanometers.

### Conclusion:
The length of one coil of B-DNA helix is **3.4 nanometers**.

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