A given double stranded DNA molecule is 1,00,000 base pairs long . The length of this DNA molecule will be

Options

A. 10,000 nm
B. `3.4xx10^4` nm
C. `10^4` nm
D. 2,00,000 nm

Answer

To find the length of a double-stranded DNA molecule that is 100,000 base pairs long, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of DNA**:
- DNA is structured as a double helix. Each complete turn of the helix measures approximately 3.4 nanometers in length.

2. **Determine the Number of Base Pairs per Turn**:
- One complete turn of the DNA helix contains about 10 base pairs.

3. **Calculate the Total Number of Turns**:
- Since we have 100,000 base pairs, we can calculate the number of complete turns in the DNA molecule:
\[ \text{Number of turns} = \frac{\text{Total base pairs}}{\text{Base pairs per turn}} = \frac{100,000 \text{ base pairs}}{10 \text{ base pairs/turn}} = 10,000 \text{ turns} \]

4. **Calculate the Total Length of the DNA**:
- Now, we can find the total length of the DNA molecule by multiplying the number of turns by the length of one turn:
\[ \text{Total length} = \text{Number of turns} \times \text{Length per turn} = 10,000 \text{ turns} \times 3.4 \text{ nanometers/turn} = 34,000 \text{ nanometers} \]

5. **Express the Length in Scientific Notation**:
- The length of the DNA molecule can be expressed in scientific notation:
\[ 34,000 \text{ nanometers} = 3.4 \times 10^4 \text{ nanometers} \]

### Final Answer:
The length of the DNA molecule is \( 3.4 \times 10^4 \) nanometers.