In purines, N is at position _____in its two rinigs.

Options

A. 1,3,7,9
B. 1,5
C. 7,9
D. 1 & 9

Answer

To solve the question regarding the positions of nitrogen in purines, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Purines**:
- Purines are a type of nitrogenous base that consist of two fused rings. The two major purines in nucleic acids are adenine and guanine.

2. **Structure of Purines**:
- Purines have a bicyclic structure, meaning they contain two interconnected rings. Each ring is composed of carbon and nitrogen atoms.

3. **Identify the Nitrogen Positions**:
- In the structure of purines, the nitrogen atoms are located at specific positions. The numbering of the atoms in the rings starts from one of the nitrogen atoms and continues around the rings.

4. **Numbering the Atoms**:
- The positions of the nitrogen atoms in purines are as follows:
- **Position 1**: Nitrogen
- **Position 3**: Nitrogen
- **Position 7**: Nitrogen
- **Position 9**: Nitrogen

5. **Conclusion**:
- Based on the structure and the positions identified, nitrogen is present at positions 1, 3, 7, and 9 in purines.

6. **Final Answer**:
- Therefore, the correct answer to the question is: **1, 3, 7, and 9**.