Question

Purines have nitrogen atoms at ______ positions.

• A. 1',3',7',9'
• B. 1',5',7',9'
• C. 1',3'
• D. 1',9'

Answer 1

The correct option is A 1',3',7',9'

The purine bases have a 9‐membered double‐ring system with four nitrogens and five carbons. The two-carbon nitrogen ring bases (adenine and guanine) are examples of purines.

So, the correct option is '1',3',7',9'.