If in a double stranded DNA, 15 pitches in a helix are present, then the number of total nucleotides in it will be

Options

A. 150
B. 300
C. 600
D. Infinite

Answer

To solve the problem of determining the total number of nucleotides in a double-stranded DNA with 15 pitches in a helix, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of DNA**:
- DNA is composed of two strands that form a double helix. Each complete turn of the helix is referred to as a "pitch."

2. **Identify the Number of Nucleotides per Pitch**:
- It is known that each pitch of the DNA helix contains approximately 10 nucleotides in each strand.

3. **Calculate Nucleotides in One Strand**:
- Since there are 15 pitches in the helix, we can calculate the number of nucleotides in one strand:
\[ \text{Nucleotides in one strand} = \text{Number of pitches} \times \text{Nucleotides per pitch} \]
\[ \text{Nucleotides in one strand} = 15 \text{ pitches} \times 10 \text{ nucleotides/pitch} = 150 \text{ nucleotides} \]

4. **Calculate Total Nucleotides in Both Strands**:
- Since DNA is double-stranded, we need to multiply the number of nucleotides in one strand by 2 to find the total number of nucleotides:
\[ \text{Total nucleotides} = 150 \text{ nucleotides (one strand)} \times 2 = 300 \text{ nucleotides} \]

5. **Conclusion**:
- Therefore, the total number of nucleotides in the double-stranded DNA with 15 pitches is 300.

### Final Answer:
The total number of nucleotides in the double-stranded DNA is **300**.

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