The width of a DNA molecule is

Options

A. 34 Å
B. 3.4 Å
C. 200 Å
D. 20 Å

Answer

To answer the question regarding the width of a DNA molecule, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Types of DNA**: Understand that there are different forms of DNA, primarily A-DNA, B-DNA, and Z-DNA. Each has distinct structural characteristics.

2. **Determine the Width of B-DNA**: The most common form of DNA is B-DNA. According to the information provided, the width (or diameter) of B-DNA is 20 angstroms.

3. **Consider Other Forms of DNA**:
- A-DNA has a width of 23 angstroms.
- Z-DNA has a width of 18 angstroms.

4. **Conclude the Most Common Width**: Since B-DNA is the most prevalent form of DNA in biological systems, the width of a DNA molecule is typically referred to as the width of B-DNA, which is 20 angstroms.

### Final Answer:
The width of a DNA molecule is 20 angstroms.

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