One turn of Z-DNA has

Options

A. 10 base pair
B. 12 base pair
C. 9.33 base pair
D. 11 base pair

Answer

To determine how many base pairs are present in one turn of Z-DNA, we can follow these steps:

### Step-by-Step Solution:

1. **Understand DNA Forms**: Recognize that DNA exists in various forms, including B-DNA, A-DNA, and Z-DNA. Each form has different structural characteristics.

2. **Identify Base Pairs in B-DNA**: In B-DNA, which is the most common form, there are 10 base pairs per turn of the helix, and the pitch length (the distance for one complete turn) is 34 Ångströms.

3. **Examine the Structure of Z-DNA**: Z-DNA is another form of DNA that has a left-handed helix structure, unlike the right-handed helix of B-DNA.

4. **Determine Base Pairs in Z-DNA**: It is known that Z-DNA has 12 base pairs per turn. This is a key characteristic that distinguishes it from B-DNA.

5. **Conclusion**: Therefore, the number of base pairs present in one turn of Z-DNA is 12.

### Final Answer:
One turn of Z-DNA has **12 base pairs**.

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