Which statement is wrong about DNA?

Options

A. Some viruses have ssDNA
B. Some viruses have dsRNA
C. Z' DNA has 12 base pairs per helix
D. Length of one helix in 'B' DNA is 45Å and 'Z' DNA is 34Å.

Answer

To determine which statement is wrong about DNA, we will analyze each of the provided options step by step.

### Step-by-Step Solution:

1. **Understanding Viruses and DNA**:
- Viruses can have either DNA or RNA as their genetic material. They are acellular and require a host to replicate.
- **Statement 1**: "Some viruses have single-stranded DNA."
- This statement is **true**. Certain viruses, like parvoviruses, indeed have single-stranded DNA.

2. **Analyzing the Second Statement**:
- **Statement 2**: "Some viruses have double-stranded RNA."
- This statement is also **true**. Examples include reoviruses, which have double-stranded RNA.

3. **Examining Z DNA**:
- **Statement 3**: "Z DNA has 12 base pairs per helix."
- Z DNA is a form of DNA characterized by a left-handed helix. It is known to have approximately 12 base pairs per turn.
- This statement is **true**.

4. **Length of Helices in DNA**:
- **Statement 4**: "Length of one helix in B DNA is 45 angstroms and Z DNA is 34 angstroms."
- The correct lengths are:
- B DNA has a length of approximately **34 angstroms** per helical turn.
- Z DNA has a length of approximately **45 angstroms** per helical turn.
- Therefore, this statement is **false** because it incorrectly states the lengths for B and Z DNA.

### Conclusion:
The wrong statement about DNA is **Statement 4**: "Length of one helix in B DNA is 45 angstroms and Z DNA is 34 angstroms."

---