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, let's analyze each statement provided in the question step by step.

### Step 1: Analyze the first statement
**Statement:** Some viruses have single-stranded DNA.
- **Analysis:** This statement is true. Certain viruses, such as parvoviruses, contain single-stranded DNA (ssDNA) as their genetic material.

### Step 2: Analyze the second statement
**Statement:** Some viruses have double-stranded DNA.
- **Analysis:** This statement is also true. Many viruses, including adenoviruses and herpesviruses, have double-stranded DNA (dsDNA) as their genetic material.

### Step 3: Analyze the third statement
**Statement:** Z-DNA has a 12-base pair helix.
- **Analysis:** This statement is incorrect. Z-DNA typically has 12 base pairs per turn of the helix, but the diameter of Z-DNA is around 18 angstroms, not the length of the helix. The statement might be misleading as it does not specify the context correctly.

### Step 4: Analyze the fourth statement
**Statement:** The length of B-DNA is 45 angstroms and the Z-DNA is 34 angstroms.
- **Analysis:** This statement is incorrect. The diameter of B-DNA is approximately 20 angstroms, and Z-DNA has a diameter of about 18 angstroms. The lengths mentioned in the statement do not correspond to the actual measurements of these DNA forms.

### Conclusion
The wrong statements about DNA are:
- The statement regarding the length of B-DNA being 45 angstroms is incorrect.
- The statement regarding Z-DNA being 34 angstroms is also incorrect.

Thus, the answer to the question is that the statement about the length of B-DNA and Z-DNA is wrong.

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