Which of the following is not a salient features of the Double-helix structure of DNA

Options

A. pitch of the helix is `10^(-9)m`
B. there are roughly 10 bp in each turn
C. the distance a bp in a relix is approximately equal to 3.4 nm
D. The plane of one base pair stacks over the other in double helix

Answer

To solve the question regarding the salient features of the double-helix structure of DNA, we will analyze each option provided and identify which one does not correctly describe a feature of DNA's structure.

### Step-by-Step Solution:

1. **Understanding the Double-Helix Structure**:
- DNA is composed of two strands that form a double helix. Each strand is made up of nucleotides, which consist of a sugar, a phosphate group, and a nitrogenous base.

2. **Identifying Key Features of DNA**:
- The nitrogenous bases pair specifically: Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C).
- The double helix has a specific pitch, which is the distance between one complete turn of the helix. This is approximately 3.4 nm.
- Each complete turn of the helix contains about 10 base pairs.
- The distance between adjacent base pairs in the helix is approximately 0.34 nm.

3. **Evaluating the Options**:
- **Option 1**: "Pitch of the helix is 10¯⁹ m" - This is incorrect because the pitch of the helix is actually 3.4 nm (or 3.4 x 10^-9 m).
- **Option 2**: "There are roughly 10 base pairs in each turn" - This is correct.
- **Option 3**: "The distance between a pair in a helix is approximately equal to 0.34 nanometer" - This is also correct.
- **Option 4**: "The plane of one base stack over the other in a double helix" - This statement is somewhat vague but generally refers to the stacking of bases, which is a feature of the double helix.

4. **Conclusion**:
- The statement that is not a salient feature of the double helix structure of DNA is **Option 1**, which incorrectly states the pitch of the helix.

### Final Answer:
**The option that is not a salient feature of the double-helix structure of DNA is: "Pitch of the helix is 10¯⁹ m."**

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