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 determine 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 a double-stranded molecule made up of base pairs. Each complete turn of the DNA helix contains about 10 base pairs.

2. **Length of One Complete Turn**:
- The length of one complete turn of the DNA helix (which includes 10 base pairs) is approximately 3.4 nanometers.

3. **Calculate the Length of One Base Pair**:
- To find the length of one base pair, we can divide the length of one complete turn by the number of base pairs in that turn:
\[ \text{Length of one base pair} = \frac{3.4 \text{ nm}}{10} = 0.34 \text{ nm} \]

4. **Calculate the Total Length of 100,000 Base Pairs**:
- Now, to find the total length of the DNA molecule that consists of 100,000 base pairs, we multiply the length of one base pair by the total number of base pairs:
\[ \text{Total length} = 100,000 \text{ base pairs} \times 0.34 \text{ nm/base pair} \]
\[ \text{Total length} = 100,000 \times 0.34 = 34,000 \text{ nm} \]

5. **Expressing the Length in Scientific Notation**:
- We can express 34,000 nm in scientific notation:
\[ 34,000 \text{ nm} = 3.4 \times 10^4 \text{ nm} \]

### Final Answer:
The length of the DNA molecule that is 100,000 base pairs long is **3.4 x 10^4 nanometers**.

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